chem geek

If one cannot consistently maintain chlorine in their pool, there are alternatives other than metal ions (mostly copper, if one is talking about algae prevention) which, as noted, can stain (especially plaster and possibly fiberglass surfaces as well as turning blond hair green).  One can add PolyQuat 60 weekly or one can use 50 ppm Borates in the pool or can use a phosphate remover though these will only take the edge off of algae growth and not necessarily prevent it completely (a phosphate remover will not remove organic phosphates so its effectiveness varies depending on what's in the pool).  Of course, one can use an automatic chlorine injection system or a saltwater chlorine generator system.

6 ppm Free Chlorine (FC) with 54 ppm Cyanuric Acid (CYA) has the same active chlorine (hypochlorous acid) concentration as a pool with 0.1 ppm FC and no CYA, not 1-1.5 ppm FC.  In this pool, over 98% of the chlorine is bound to CYA.  This not only comes from the core science known since at least 1974 in the [url=http://richardfalk.home.comcast.net/~richardfalk/pool/OBrien.htm]O'Brien paper[/url] that determined the equilibrium constants, but it's also consistent with the lowering of kill times for bacteria, inactivation of viruses and protozoan oocysts, rate of oxidation of organics, and lowering of ORP levels as well as algae inhibition rates (from the experience of tens of thousands of pool owners; not from the one scientific paper on this).  This is all documented in [url=http://www.troublefreepool.com/certified-pool-operator-cpo-training-what-is-not-taught-t18432.html]this post[/url] in the "Chlorine/CYA Relationship" section.  Fortunately, it takes very low levels of active chlorine to kill most pathogens and somewhat more to prevent algae growth (such levels being in the [url=http://www.troublefreepool.com/pool-school/chlorine_cya_chart_shock]Chlorine / CYA Chart[/url]). Richard

[quote user="allanb"]I'm trying to convince myself that I don't really need to spend £100+ to find out what I need to know. I have bought an Aquachek kit which uses test strips.  It really is spelled like that, without the second 'c' - I presume that we're talking about the same manufacturer: Hach Company from Elkhart, Indiana.  It cost me less than €10, IIRC.  It claims to measure 4 things: free chlorine and cyanuric acid, mentioned by Poolguy, and also pH and total alkalinity. Now I can understand that colour strips may be less convenient and less accurate than something with a digital readout, for instance.  But does that really mean that they are useless?  Is the Hach Company lying when it says that the kit measures those four things? Or is Aquachek something different from Aquacheck? I'm confused.[/quote] There is a lot more than just "what it tests", but also "does it test accurately" and "to what precision".  Let's take a closer look at the [url=http://www.aquachek.com/products.asp]Aquachek® Yellow[/url] that tests for Free Chlorine, Cyanuric Acid, pH and Total Alkalinity. The [url=http://www.taylortechnologies.com/products_kitinfo.asp?&MarketID=-1&KitID=2230]Taylor K-2006[/url] test kit uses a FAS-DPD chlorine test where you count the drops until the sample turns from pink/red to clear.  It can measure up to 50 ppm and does not bleach out at high chlorine levels (unlike test strips and DPD chlorine tests).  It can measure with a resolution AND accuracy of 0.2 ppm when using a 25 ml sample size, though usually you use a 10 ml sample size for 0.5 ppm resolution and accuracy.  The Aquachek does what?  Go ahead...take a look at the range and resolution. The pH test is similar to a test strip (they tend to be OK with pH) though has comparator examples of 7.0, 7.2, 7.4, 7.6, 7.8, 8.0. The Total Alkalinity (TA) test has a resolution AND accuracy of 10 ppm -- look at your test strips and see that they only roughly estimate TA -- probably only within 40 ppm. The Cyanuric Acid test is a tricky turbidity test, but has an accuracy of around 10-15 ppm depending on where you are in the CYA scale and measures up to 100 ppm (you can measure higher with a diluted water sample). The Taylor K-2006 also has a Calcium Hardness (CH) test that no test strip has (some test strips test for Total Hardness, but that includes Magnesium). If you have a plaster pool or a pool with exposed grout to the water, then you really need to know the CH level and the other levels to calculate the saturation index to protect such surfaces. The experience of thousands of pool owners at both [url=http://www.poolforum.com/pf2/index.php]The PoolForum[/url] and [url=http://www.troublefreepool.com/]Trouble Free Pool[/url] is that pool store testing and test strips are not very accurate in general, most especially for the CYA test though other tests vary a lot as well.  pH is about the only one that is usually reasonable. Richard

The USA tends to over-promote the use of stabilized chlorine products (Trichlor tabs/pucks, Dichlor powder for "shock") which leads to algae growth in many pools from a buildup of Cyanuric Acid (CYA).  I wouldn't assume that anything from the USA is necessarily better -- it's just more likely to be more profitable for manufacturers.  Product offerings are driven more by economics than what is best for the consumer.  I'm not bashing; I live in the U.S., but one can't deny the truth. The best test kit at a reasonable price is the Taylor K-2006 which in the U.S. can be obtained online [url=http://www.amatoind.com/taylor-k2006-test-p-555.html]here[/url].  It tests for Free Chlorine (FC) and Combined Chlorine (CC) using a FAS-DPD chlorine test where you count the drops until the sample turns from pink to clear as shown in the demo [url=http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=11]here[/url].  It does not bleach out and can measure up to 50 ppm and can be accurate to within 0.2 ppm when using a 25 ml sample size (0.5 ppm when using a 10 ml sample size).  It also tests for pH, Total Alkalinity (TA), Calcium Hardness (CH) and Cyanuric Acid (CYA) generally with 10 ppm accuracy (CYA is a little tricky but still far better than test strips).  A similar alternative is the TF-100 kit from [url=http://tftestkits.net/Test-Kits-c4/]tftestkits.net[/url]. Test strips, even those used by your AquaChek meter, cannot test for Calcium Hardness.  They only test for Total Hardness which is pretty much totally useless since it is calcium and not magnesium that is needed to protect plaster surfaces from dissolving and to not get too high to prevent scaling.  The CYA test is also very often wrong when using test strips. In Europe, the closest test kit to the Taylor K-2006 that I've been able to find is the Palintest Pooltester SP 315C that does all of the aforementioned tests, BUT uses a DPD chlorine test.  At least in the U.S., Palintest has introduced a FAS-DPD chlorine test as described [url=http://www.palintestusa.com/products-details.aspx?id=72]here[/url].  The Palintest meters that Andrew offers are also good so you have to weigh cost vs. convenience.

Unfortunately, the terminology for what "Free Chlorine" means has changed over the years.  When the chlorine/CYA relationship was definitively determined in [url=http://richardfalk.home.comcast.net/~richardfalk/pool/OBrien.htm]this scientific paper[/url] back in 1974, the term Free Chlorine meant the hypochlorous acid (the killing form of chlorine) and the hypochlorite ion (not very effective at killing), but not the chlorine bound to CYA (technically called chlorinated isocyanurates).  This paper called the sum of the Free Chlorine and the chlorine bound to CYA as reservoir chlorine since it was chlorine held in reserve that was available (i.e. releaseable) as the hypochlorous acid got used up killing pathogens or oxidizing bather waste or other organics. At some point in time, test kits started referring to "Free Chlorine" as what was being measured in the DPD or the FAS-DPD tests.  These tests actually measure what used to be called reservoir chlorine because the chlorine bound to CYA gets released in the timeframe of these tests.  So you are really measuring not only the active chlorine, hypochlorous acid, but also the chlorine in reserve as hypochlorite ion and mostly the chlorine bound to CYA. Combined Chlorine (CC) is chlorine bound to ammonia (as chloramines) and organics (such as chlorourea) that get measured in the DPD test after adding potassium iodide (that's what DPD3 does).  Most chlorine bound to ammonia or organics will oxidize the iodide to iodine that then reacts with the dye in the test.  Technical details about these sorts of tests are in [url=http://www.hach.com/fmmimghach?/CODE:L70191473%7C1//true]this paper[/url]. It is the Combined Chlorine (CC) that can be smelly and irritating, especially the chloramines and of those most especially nitrogen trichloride. One can consider CYA to be an active chlorine (hypochlorous acid) buffer, holding most of it in reserve.  This means that the amount of active chlorine is much lower when CYA is present and roughly speaking at a pH near 7.5 a pool with an FC and CYA is roughly equivalent to a pool with FC/CYA as FC and having no CYA.  So, a pool with 3 ppm FC and 30 ppm CYA, for example, has roughly the same active chlorine concentration as a pool with 0.1 ppm FC and no CYA.  Fortunately, it takes very little active chlorine to kill pathogens and to oxidize bather waste reasonably quickly, but this also means that pools that don't use any CYA are typically over-chlorinated which can lead to a greater production of nitrogen trichloride, faster oxidation of swimsuits, skin and hair, faster corrosion rates, etc.  This is one reason the German DIN 19643 standard specifies 0.3 to 0.6 ppm FC with no CYA (0.2 to 0.5 ppm if supplemental ozone is also used) though this is still at least 2-3 times higher than the FC as 10% of the CYA example I gave.  Higher active chlorine levels may produce more nitrogen trichloride (I write about this technically [url=http://www.troublefreepool.com/chloramines-and-fc-cya-t10257.html]here[/url]). Richard

That would be me, but I would normally recommend using chlorinating liquid or 6% unscented bleach even for regular dosing unless one cannot add chlorine every day or two (unless they have a pool cover in which case they can add it around twice a week).  The automated dosing systems such as what Andrew sells are the most convenient (well, except possibly for a saltwater chlorine generator system). The only time you'd want to use Trichlor pucks/tabs is if your Cyanuric Acid / stabilizer / conditioner level is too low or you just have to have the convenience of using these tabs since they slowly dissolve (such as on a one-week vacation).  If you use Trichlor as your primary source of chlorine over time, then you'll have to do something to manage the rising Cyanuric Acid / stabilizer / conditioner level since it is only reduced by dilution.  If you don't dilute the water, then one can use an algaecide or phopshate remover (both at extra cost) to prevent algae growth. Richard

Yes, but being a manufacturer's website, they don't tell you how quickly the use of Trichlor or Dichlor products can increase your Cyanuric Acid / stabilizer / conditioner level.  For example, even if you have a relatively low 1 ppm Free Chlorine per day chlorine usage, if you use only Trichlor pucks/tabs as your source of chlorine then after just 6 months you will have increased your Cyanuric Acid / stabilizer / conditioner level by over 100 ppm.  Only significant water dilution would limit this somewhat, including regular backwashing of a filter, significant splash-out, rain overflow or intentional partial drain/refill. In my own pool 6 years ago, my Cyanuric Acid / stabilizer / conditioner level rose from 30 ppm to 150 ppm in just 11 months of in-season use (over one and a half seasons) from using Trichlor alone.  This was with a pool that only used 0.8 ppm Free Chlorine per day due to an opaque safety cover, but I had an oversized cartridge filter so had no backwashing and I had a pool cover pump so didn't dilute the water with winter rains (because at that time, I didn't know anything about these things). If you were to read the manufacturer's website, you'd never know why Andrew's chlorine injection system is a superior method unless you want to spend extra money on algaecides or phosphate removers to control algae growth.  In my 16,000 gallon pool (shown [url=http://richardfalk.home.comcast.net/~richardfalk/pool/PoolDay.jpg]here[/url]), I use 12.5% chlorinating liquid I buy from my local pool store that I add to the pool twice a week and it costs me $15 per month.  They reuse the containers which is better than recycling.  My pool's pH is very stable so I only need to add a small amount of acid every month or two.  That's it.  No other chemicals needed during most of the season (only touch-up from dilution from winter rains once a year). Richard

Normally, a saltwater chlorine generator (SWG) pool will tend to rise in pH over time and require acid addition to keep the pH at around 7.5 which is the average pH of human tears (though anything from 7.2 to 7.8 is usually OK).  The rise is due to a combination of carbon dioxide outgassing and some undissolved chlorine gas outgassing.  Though it is certainly possible that your SWG unit is malfunctioning or undersized for the size of your pool, there are other possibilities.  First, is that your Free Chlorine (FC) level may be too low for your Cyanuric Acid (CYA) level.  In an SWG pool, the FC target minimum should be at least 4.5% of the CYA level.  Otherwise, green algae can grow faster than chlorine can kill it and initially this may appear as an unusual chlorine demand (i.e. the algae is not yet visible, yet it is hard to maintain an FC level).  Second, is that your CYA level may be too low in which case your FC is dropping too much each day from the UV rays in sunlight. You can easily distinguish between these two scenarios by doing an overnight test to see the drop in FC from after the sun is off the pool at night until the sun starts to hit the pool in the morning (or as early as you can muster getting up!).  Such FC drop tests are done with the SWG turned off and you raising the FC level using chlorinating liquid (or 6% unscented bleach, if you cannot find liquid chlorine).  If you find an FC drop of more than 1 ppm, then you've likely got algae growth so the FC/CYA ratio is too low and you need to target a higher FC level (after shocking the pool first with a higher FC to kill off the algae quickly).  If the overnight FC drop is low and your CYA level isn't high (i.e. 60-80 ppm) and if you find the daytime FC drop is high (> 2 ppm) then you need to raise the CYA level (and your target FC level along with it). Many SWG manufacturers (at least in the U.S.) recommend a 1-3 ppm FC with 60-80 ppm CYA, but this is not sufficient to prevent algae growth in some pools (ones rich with algae nutrients; phosphates and nitrates).  Having a target of at least 3.6 ppm FC with 80 ppm CYA (say 4 ppm FC to make things simple) will work. If you want to maintain a lower FC then the roughly 5% of CYA target, then you would need to use supplemental chemicals at extra cost (i.e. weekly PolyQuat 60 algaecide, or a phosphate remover, etc.).  Another approach that just involves a mostly one-time dose is to add 50 ppm Borates to the pool.  This acts as an additional pH buffer, but also is a mild algaecide.  You can read more about [url=http://www.troublefreepool.com/pool-school/water_balance_saltwater_generator]Water Balance for SWGs[/url]. Richard

The guideline used in the U.S. for the Water Replacement Interval (WRI) for commercial/public spas is: WRI (days) = (1/3) x (Spa Volume in U.S. Gallons) / (Number of Bathers per Day) The presumed soak time is around 20 minutes and the temperature is hot (100-104F).  The above translates into changing 3 gallons of water for every bather use.  In a pool, the amount of sweat/urine relative to a spa is probably around half, but people stay in the pool longer.  In commercial/public pools, the water replacement is at 7 gallons for every bather but this is continual replacement and roughly translates to 1.5 gallons of absolute replacement (i.e. if 7 gallons represented 99% effective water replacement, then this is equivalent to an absolute 1.5 gallon replacement without continuous dilution).  DIN 19643-1 says 30 liters of (continuous) water replacement which is roughly 8 gallons. Your 8 foot round 2 foot deep "pool" is around 100 cubic feet or 750 gallons.  The WRI from the above formula for 2 bathers would be 125 days or around 4 months.  However, kids tend to urinate more in pools and they may stay in the pool for a longer time.  Nevertheless, there should be no need to change the water every few days.  I would think you could go for at least a month and be OK.  As PoolGuy (Andrew) mentioned, just treat the water as you would any pool.  Have some Cyanuric Acid (CYA) in the water to protect the chlorine from sunlight and to moderate the chorine's strength and then just maintain sufficient Free Chlorine (FC) in the pool so that it is sanitary.  pH and TA should be maintained as well. Richard

I just want to note that bicarbonate of soda (aka baking soda or sodium bicarbonate or sometimes called sodium hydrogen carbonate) is mostly used for raising the Total Alkalinity (TA) and isn't the best choice for raising the pH unless you really do want to raise the TA a lot.  To raise the pH with less of a rise in the TA, you can use washing soda aka sodium carbonate.  In the U.S. this is found in the grocery store as Arm & Hammer Super Washing Soda.  If you want to raise the pH with even less of a rise in TA, you can use borax which in the U.S. is 20 Mule Team Borax (sodium tetraborate decahydrate) or you can use caustic soda (aka lye or sodium hydroxide).  These chemical choices have widely different concentrations so you can use [url=http://www.thepoolcalculator.com/]The Pool Calculator[/url] for rough dosing (dosing for pH adjustment is an approximate calculation in this calculator). Richard

Test strips are OK for some measurements, but for others they aren't very good and from what I've seen from posts of those who have used them, CYA doesn't get measured very well in the test strips.  The melamine turbidity test is better, though even that is somewhat subjective (though probably within +/- 10 ppm).  It's in Taylor kits as shown [url=http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=44]here[/url].  You can get a great test kit including just a CYA test from tftestkits.net [url=http://www.tftestkits.net/index.php?act=viewProd&productId=24]here[/url] or the full TF100 [url=http://www.tftestkits.net/index.php?act=viewProd&productId=2]here[/url] but with shipping it won't be cheap.  I am not familiar with what you've got available in France.

Giles, The graph you refer to [url=http://www.pool-technologie.com/en/pool-treatment/ph-regulation-2.html]here[/url] is in fact misleading.  It is the same as a middle portion of the red curve in the first graph in my post [url=http://www.troublefreepool.com/post50548.html#p50548]here[/url] which is the traditional industry graph showing the active chlorine (hypochlorous acid) concentration as a function of pH. This may be one of the reasons they want the pH lower at 7.0, but there are several problems with that approach.  First, is that it is harsher on the eyes since typical tears have a ph of 7.5.  Second, it is somewhat harsher on equipment since lower pH is more corrosive.  Third, lower pH will tend to outgas carbon dioxide faster causing the pH to rise more quickly requiring more acid to keep the pH low (see [url=http://richardfalk.home.comcast.net/~richardfalk/pool/CO2.htm]this chart[/url]).  Fourth, their graph does not apply to chlorine's effectiveness when there is Cyanuric Acid (CYA) in the water.  In my post, I show the correct graph to the right of the traditional industry graph.  I also show a pair of log graphs that show the "flatness" of the red curve without CYA (on the left) and when CYA is present (on the right).  Essentially CYA is a buffer for the active chlorine (hypochlorous acid) so changes in pH don't affect the effectiveness nearly as much as without CYA. Andrew's point about the CYA level is spot-on.  If your pool is exposed to direct sunlight, then the CYA level can have a very dramatic effect on the rate at which chlorine is broken down by the UV in sunlight and therefore the rate at which chlorine needs to be produced by PoolSquad.  You will make your PoolSquad plates last longer and you will reduce the rate of pH rise in your pool (and use less acid) if you are able to lower the on-time of your PoolSquad.  You can do that by having a higher CYA level in the pool. Now here's where Andrew and I might disagree.  Some pool owner experiences plus some experiments that were made show that having a much higher CYA level of around 70-80 ppm can significantly lower the amount of chlorine loss even if one proportionately raises the Free Chlorine (FC) target to 4 ppm in order to prevent algae growth (without the need for a supplemental algaecide or phosphate remover) in a saltwater chlorine generator (SWG) pool.  However, if you usually keep a pool cover on the pool, then a CYA level in the 30-50 ppm range should be adequate with a minimum FC level of around 5% of the CYA level. If you wanted to have some extra algae prevention, you could use 50 ppm Borates in the pool as this is not only an additional pH buffer, but is also a mild algaecide (algistat).  This extra pH buffering will also reduce calcium scaling in the PoolSquad cell (I hope that their product alternates polarity periodically to help keep the plates free of scale). Richard

Andrew, So I called up Dr. Ian Leahy early this morning my time (about 2:15 AM so I would catch him in the office) long-distance from U.S. to England and after I explained what I had written he said I wasn't half-right but was completely right.  He only very quickly reviewed my post you referred him to and did not realize that I was already saying that the indophenol test measures both (the sum of) monochloramine AND ammonia.  He agreed that in pools with chlorine (that is, Free Chlorine) there should be effectively no measurable ammonia because chlorine combines so quickly with ammonia to form monochloramine so any measurement in the indophenol test in such pools would be that of monochloramine.  He also confirmed that the indophenol test itself actually measures monochloramine and that the first step in the test adds chlorine to convert any ammonia to monochloramine for the subsequent steps and measurement.  That's why the test overall measures the sum of ammonia and monochloramine. So except for pools where the Free Chlorine (FC) measurement is zero, please stop saying you are measuring ammonia in the pools -- because you aren't.  In pools with measurable FC, your indophenol test is measuring monochloramine (because there is effectively no ammonia). Also, I asked Dr. Leahy about whether the Palintest reported in units of ppm-N as with ammonia or ppm-Cl2 as with chlorine or monochloramine since you reported such high numbers (e.g. 4.56 and 5.65).  He said that if you were using a Palintest instrument for the measurement, that "the nominal range of the instrument is 0 - 1 mg/l N so some dilution has been made and the high results may stem from that (either the diluent or the calculation)."  So can you please tell me exactly how you are doing the measurement since the instrument itself would only report up to 1 mg/L?  How are you getting your 4.56 and 5.65 numbers? By the way, in the signature in the E-mail I received (I asked him a separate question via E-mail), the name is "Ian Leahy" without an "e" before the "y" and his title is "Export Sales Executive" though when I talked to him he clearly understood chemistry so may be their chemist as well (I didn't ask). Richard

[quote user="Poolguy"][quote user="chem geek"]Otherwise, you just end up measuring the sum of monochloramine and ammonia -- not ammonia alone.   It should be obvious that if you already have monochloramine, then that is going to be additionally measured in the test.  It should also be obvious that the test itself counts on the fact that the first step, where ammonia and chlorine combine to form monochloramine, occurs quickly. [/quote] "I read the thread that you pointed me at and your detractor is half right with all the interesting text book information about reaction times and species formed but wrong about the scope of the indophenol test we use for ammonia.   The ammonia test using the indophenol method will pick up all the free ammonia and the monochloramine. The monochloramine is a volatile amine and at swimming pool pH is the main variant of chloramine produced. The only variant of ammonia that you will be missing is the dichloramine which can be determined using the DPD test method if you want to go so far but I don't think that is necessary." I am satisfied (at least) that the testing that I am doing is correct as it is advertised by Palin test to be an test of Free Ammonia present in Swimming pools [/quote] Andrew, Please re-read the response from Palin.  It is EXACTLY as I had described it (I don't know what they think is "half right").  The test you are using measures, and I quote Dr. Leahy, "free ammonia and the monochloramine".  Read that again until you see the words "and the monochloramine".  You cannot claim you are measuring ammonia with the test because it measures, and I quote this again, "free ammonia and the monochloramine". Monochloramine is somewhat volatile, but not THAT volatile, especially when compared to nitrogen trichloride.  The Henry's Law constant (see [url=http://www.mpch-mainz.mpg.de/~sander/res/henry.html]here[/url]) for hypochlorous acid is around 930, for monochloramine it is around 94, for ammonia it is around 60, for dichloramine it is around 29, and for nitrogen trichloride it is around 0.1 where lower numbers are more volatile (equilibrium is more towards gaseous state than being dissolved in water).  The fact that one can even measure monochloramine in the DPD test fairly readily shows that it can't be so volatile as to not be measurable in pool water. So please stop saying that you are measuring ammonia in every pool, at least those with measurable (non-zero) Free Chlorine (FC).  With the test you are using from Palin, you are measuring "free ammonia and the monochloramine" and are NOT distinguishing between the two.  You do not know whether you are measuring monochloramine or measuring ammonia since the test measures the SUM of the two!  This is what I had said and what Dr. Leahy confirmed. Thank you for explaining details about the "Andy" pool and if after circulation the results are lowered then that would be a better confirmation of lower "free ammonia and the monochloramine", BUT realize that if there is no chlorine and there is ammonia, then adding chlorine will get rid of the ammonia through breakpoint chlorination and that will have nothing to do with the filter.  So the best pools to use would be those with measurable FC yet have CC or "ammonia" (really monochloramine) amounts and that this is lower in Zeolite filter pools than in sand filter pools. If you would please use the DPD or even better FAS-DPD test to check not only the Free Chlorine (FC) level, but also the Combined Chlorine (CC) level of the pools you are testing, then that would help determine whether it is ammonia or monochoramine that you are measuring.  When there is no Free Chlorine (FC) in the water (such as in the Andy pool), then ammonia can be present and you can be measuring that (monochloramine could be present as well if there was some chorine earlier).  When there is Free Chorine (FC) in the water, then there will be no measurable ammonia present so what you are measuring is monochloramine.  This is where the DPD or FAS-DPD CC test comes in since that will measure monochloramine and not ammonia though unfortunately also measures other CC as well such as chorine combined with urea. The bottom line is that if you show most or all of the pools with lower levels in your "ammonia" test or your CC test, then that's a good thing but does not mean there was ammonia in the pools at the time of your testing.  It means there was ammonia OR monochloramine (or a combination) in the pools (and if you measure non-zero FC, then I'm saying that it's monochloramine that you are measuring).  The fact that the zeolite helps lower the monochloramine level is still a good thing, but it is not because there is ammonia in the pool and that is what I was disputing since that is what you were originally claiming.  As I said earlier, the lower monochloramine can also come from better (finer) filtration which other filters (DE, AFM, etc.) could provide removing more precursors that could combine with chlorine.  Also, sand filters can get bacterial fouling which could increase CC levels (if Dryden is correct). Again, chlorinated pools, those with measurable FC, do not have ammonia in them (except immeasurable equilibrium amounts), but may have monochloramine and other combined chlorine. By the way, you never answered my question about what "green" meant.  Does that mean the pool is "green" meaning algae or that the ammonia test showed green?  Does that mean these pools have no chlorine in them (i.e. FC is zero)?  There isn't much point measuring pools without chlorine since that isn't how you are supposed to maintain a pool.  If one lets a pool go over the winter and doesn't maintain chlorine levels, then one can certainly end up with an algae bloom or have bacteria convert CYA into ammonia and one can end up measuring lots and lots of ammonia and monochloramine.  The value of a filter reducing monochloramine levels (through whatever means) is when the pool is being chlorinated, so when there is measurable FC. Richard

[quote user="Poolguy"] I do not accept your statement that the thousands of pools country wide have been operating acceptably - as chemical analysis I have done (and will continue to do) proves that they are not, due to in part an excess or ammonia present in the water which is not dealt with by sand but is extracted by Zeolite. [/quote] Andrew, If you want to claim from the small sample of pools that it appears that there is a lower amount of monochloramine in pools using zeolite, then that is one thing (though one pool measured high even with zeolite), but if you measured any Free Chlorine (FC) in the pool then do not claim your results measured ammonia.  As Palintest will tell you (I suggest you call them if you have not already) your testing for ammonia was interfered with monochloramine -- the test you were using tests both monochloramine and ammonia combined.  It was designed to measure ammonia in unchlorinated water, not in pools with chlorine. Next time you measure a pool with your test, try measuring also the Combined Chlorine (CC) with a FAS-DPD chlorine test (for accuracy) in addition to your "ammonia" test. I have a cartridge filter in a 16,000 gallon pool used daily by 1 person for 1-2 hours and on weekends by 2 people for around 2 hours and I frequently measure both Free Chlorine (FC) and Combined Chlorine (CC) with the latter always being less than 0.4 ppm and usually being less than 0.2 ppm (the lowest measurable in the FAS-DPD test I use).  This is typical for most outdoor residential pools.  I would assume that the pools you are measuring have high bather load or are indoor or much smaller pools in order to have such high CC which your ammonia test picked up (unless the FC was zero in which case the pool is not properly maintained). Richard

[quote user="buckdendave"]The trouble with ClO2 is that it such a powerful oxidising agent that it has the ability to be destructive - for the same kind of reason that its so effective at dismantling pathogens.  We have been doing a lot of work with it in our test loops and it has the ability to destroy the loops at any significant level, especially as temperature rises.  You can be sure that any gaskets or seals are going to be attacked PDQ, for example.  Everything has to be fluoropolymer based if its going to last.  (Yes I'm a polymer chemist) [/quote] Thanks Dave.  That's good to know.  Since fecal accidents with loose stools are somewhat infrequent, I would hope that a shock with 1 ppm chlorine dioxide wouldn't be too destructive to equipment, but I see your point that it wouldn't be good as a regular sanitizer even if its other problems were solved.  I actually got the idea of using sodium chlorite by noticing that there were drinking water sanitation tablets sold in camping stores that used a combination of sodium chlorite and Dichlor.  After looking up the chemistry, I then noticed that there used to be sodium chlorite products (tablets, I think) to add to pools to produce chlorine dioxide, but I also noticed these pool tablets aren't available anymore.  This is probably due to the problems you mention as well as the others I referred to.  One also has to carefully dose the chlorite with the chlorine or else too many by-products are formed. For an overnight shock after a fecal incident, the idea would be to either let sunlight breakdown the chlorine dioxide or one would use a reducing agent (dechlorintaor) before adding chlorine again.  The FC level for a Crypto kill using chlorine is 10 ppm FC with no CYA for 25 hours.  I suspect that won't be very good for pump seals or other components either.  What was the chlorine dioxide concentration when you saw problems and how long was the exposure?

Unless the pool is covered or otherwise not in direct sunlight, having no stabilizer in the water will have the chlorine get broken down by the UV in sunlight very quickly -- with no Cyanuric Acid (CYA) at all, half of the Free Chlorine (FC) will get used up around every 30 minutes or so.  Your SWG might struggle to keep up. If you can't find Cyanuric Acid itself, you can use Dichlor granular/powder since for every 10 ppm FC that it adds, it also increases CYA by 9 ppm and it dissolves quickly (unlike pure Cyanuric Acid that is slow to dissolve).  So you could just use Dichlor as your chlorine source until you've cumulatively added enough to get the CYA up. By the way, did you close your pool with measurable CYA?  Did you let your pool go over the winter without adding any chlorine?  If the answer to both questions is yes, then soil bacteria that got into the water could have converted the CYA into ammonia (and other intermediate compounds) which would look like an insatiable chlorine demand.  It could take a large amount of chlorine to get rid of the ammonia and related compounds.  I suggest you do a bucket test to find out.  Take a large bucket of pool water and add a very small amount of chlorine to it and see if after 30-60 minutes it measures FC.  For example, 1 ml of 6% bleach in 8 liters should result in 7.7 ppm FC. From your posts, I'm not clear if, after April, 2008, you ever tried adding chlorine manually to get a reading and were ever successful.  You concluded that your SWG wasn't working, but unless you were able to add chlorine manually and get an FC reading, then that was not the right conclusion. As for bleaching out the standard DPD chlorine test, you have two options.  The simplest and least expensive is to also get an OTO chlorine test -- the one that has a comparator that shows yellow (instead of the pink/red of the DPD test).  Though this isn't as accurate a chlorine test, it doesn't bleach out so would at least confirm whether there is chlorine in the water or not.  Another alternative, that is the best and most accurate test for chlorine in a reasonably priced kit, is the FAS-DPD chlorine test as shown in a demo [url=http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=11]here[/url].  It measures to within 0.2 ppm for Free Chlorine (FC) and Combined Chlorine (CC), does not bleach out, and can measure up to 50 ppm.  I don't know if you can get such a kit in France, however. Richard

Chlorine dioxide is a good water treatment alternative.  The EPA has a good summary on its use [url=http://www.epa.gov/ogwdw/mdbp/pdf/alter/chapt_4.pdf]here[/url].  Where we live, monochloramine is used as a residual, but we have an activated carbon water filter that removes it (and it used to remove chlorine when that was used insetad of monochloramine) so the water tastes fine after the filter. In fact, were it not for chlorine dioxide being so sensitive to breakdown in sunlight and it being difficult to dose/administer (especially in ways that avoid forming chlorate), it would be used in more pools as well.  Since it's so much better than chlorine at killing Crytpo, I've suggested using sodium chlorite added to chlorinated water that has CYA in it (that combo produces chlorine dioxide) as an overnight "shock" after a fecal accident since it can be used at 1 ppm over 8 hours, but since I'm pretty much a nobody, I don't think anyone is considering this.  With chlorine alone, one has to get to 10 ppm for 25 hours and that's without CYA in the water -- with CYA, the use of chlorine to shock after a fecal accident starts to become impractical.  See the [url=http://www.cdc.gov/healthyswimming/pdf/Fecal_Incident_Response_Recommendations_for_Pool_Staff.pdf]Fecal Incident Response Recommendations for Pool Staff[/url]. Richard

[quote user="teapot"] The reason why Zeolites can filter out Ammonia is due to the ion exchange that takes place inside the filter, bearing in mind that water companies add somwhere in the region of 0.5mg/litre to the supply water it's not surprising its found in the pools. The majority of ammonia comes from the bacteria that convert Urea that comes from humans. [/quote] No one is disputing that zeolite filters out ammonia.  The issue is whether ammonia persists long enough in the presence of chlorine in order to be filtered out (it doesn't). Water supplies do not add ammonia alone.  Those water companies that no longer add chlorine as a residual now add monochloramine (rapidly formed from a combination of adding chlorine and ammonia).  A recent study comparing chlorine and monochloramine effects in water supplies is [url=http://www.medicalnewstoday.com/articles/64342.php]here[/url]. Also, as described on p. 62 (PDF page 85) [url=http://www.who.int/entity/water_sanitation_health/bathing/bathing2/en/]here[/url], the largest nitrogenous component of sweat and urine is urea, followed by ammonia.  It is true that bacteria can convert urea to ammonia, but in a properly sanitized pool (i.e. one with residual chlorine) this should not happen since bacteria are quickly killed by chlorine.  Instead, chlorine oxidizes the urea, though this happens rather slowly taking many hours to days (though may be accelerated by UV from sunlight).  Chlorine oxidation of ammonia is much faster taking hours (at typical chlorine levels with CYA in the water). Richard

Andrew, The indophenol method is described [url=http://www.hach.com/fmmimghach?/CODE%3AMETHOD10200_40006110%7C1]here[/url] where the test for ammonia actually creates monochloramine so one must first measure the monochloramine amount before going further with the test to measure ammonia.  Otherwise, you just end up measuring the sum of monochloramine and ammonia -- not ammonia alone.  This is also described [url=http://www.chemetrics.com/analytes/ammonia.html]here[/url] (the second test -- salicylate method -- salicylate is a phenol; these tests are also described [url=http://www.hach.com/fmmimghach?/CODE%3AEX_NITROGENAMM1436%7C1]here[/url]).  In other words, you have to subtract the monochloramine amount from the ammonia amount (in similar units) or re-zero the measuring device in two steps as described in the Hach instructions.  The Palintest description [url=http://www.palintest.com/products-details.aspx?id=14]here[/url] (and in the ammonia section [url=http://www.completeleisure.ie/elements/download/palintest_comparitor.pdf]here[/url]) implies that these tests are designed for non-chlorinated waters.  If your specific test instructions didn't say to first measure monochloramine and account for that in the test, then monochloramine interefered with your result -- in fact, you likely just measured monochloramine (and technically, according to [url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TF4-4S7SV5B-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a61791f39ab386ce23efd26e945c9262]this link[/url] it's literally monochloramine, inorganic chloramine, and not any organic chloramines such as chlorourea).  The Hach instructions give a nice summary of the test method as follows where it is clear that the test is really for monochloramine and that one creates monochloramine from ammonia using chlorine (that clearly reacts quickly since you only have to wait for 2 minutes at 25C or 77F): Summary of Method Monochloramine (NH2Cl) and “free ammonia” (NH3 and NH4+) can exist in the same water sample. Added hypochlorite combines with free ammonia to form more monochloramine. In the presence of a cyanoferrate catalyst, monochloramine in the sample reacts with a substituted phenol to form an intermediate monoimine compound. The intermediate couples with excess substituted phenol to form a green-colored indophenol, which is proportional to the amount of monochloramine present in the sample. Free ammonia is determined by comparing the color intensities, with and without added hypochlorite. Figure 1 in [url=http://www.hach.com/fmmimghach?/CODE%3AL61351472%7C1]this PDF file[/url] shows the chemical reactions in the test where the first step is to convert any ammonia to monochloramine.  It should be obvious that if you already have monochloramine, then that is going to be additionally measured in the test.  It should also be obvious that the test itself counts on the fact that the first step, where ammonia and chlorine combine to form monochloramine, occurs quickly. Also, if you have no chlorine in the pool water, then obviously any ammonia will persist as ammonia and will get measured as such.  It looks like one pool may have had that situation.  It looks to me like you ended up measuring the amount of monochloramine and not ammonia in the water, except possibly for the pool that had "no chlor" (what did you mean by this -- no chlorine?). Ammonia is typically measured as mg NH3-N / L which is units of atomic nitrogen.  Monochloramine is typically measured as mg Cl2 / L which is units of chlorine gas equivalent.  There is roughly a factor of 5 difference in these measurements.  That is, 0.2 ammonia results in 1.0 monochloramine.  If your measurements of 5+ ppm ammonia were correct and measured in atomic nitrogen units, then if chlorine were present this would result in 25+ ppm monochloramine which seems unlikely.  Your "Andy" measurement was high at 5.65 yet used zeolite and said "no chlor" which I presume means no chlorine.  If that is the case, then with the zeolite there should not have been such a high ammonia so I strongly suspect that you were in fact measuring monochloramine in your tests and not ammonia.  Are you sure you did the test correctly? The Nessler method (see [url=http://www.ungiwg.org/openwater/?q=node/82]here[/url]) does not get interference from monochloramine since the sample is dechlorinated [EDIT] actually, not true -- I see that it too gets interference from chloramines, probably because dechlorination converts monochloramine to ammonia [END-EDIT].  The Nessler reagent uses mercury, however, and is a more complex test to perform. If I assume that you did the test incorrectly (or used the wrong test -- one that was not designed for chlorinated waters) and instead measured monochloramine, then your small sample does indicate a possibly lower likelihood for monochloramine (at least as measured) when zeolite is used, at least when chlorine is present.  Remember that I said that it was possible for a finer filtration to remove more organic precursors that could form chloramines.  That would be somewhat consistent with your data, though any filter with finer filtration would theoretically have the same result.  In other words, it doesn't have anything to do with ammonia absorption in the zeolite. Can you give more specific details about how you did the test and distinguished between monochloramine and ammonia?  Did you tell your contact at Palintest that you were going to be testing swimming pool water that was chlorinated and therefore could contain monochloramine and whether their test would be interfered by this or, in effect, measure the sum of ammonia and monochloramine?  Do you have any links or references to the "vast body of Doctorial research" you refer to?  Also, why were so many pools "green" in your comments?  Do you mean they had algae?  Pools with algae and with chlorine (though obviously too low for the CYA level) will often measure high in Combined Chlorine (CC), mostly from monochloramine. As for how fast chlorine combines with ammonia to form monochloramine, it's only a few seconds when the chlorine is strong due to no CYA in the water.  When the FC is roughly 10% of the CYA level, then the reaction is 90% complete in a little under one minute at 25C (77F) temperature.  The chlorine that is typically used in the indophenol test is typically Dichlor or some mixture of hypochlorite with CYA in order to slow down the reaction since you don't want to end up oxidizing the monochloramine during the time of the test. Richard

Most people who have saltwater chlorine generator (SWG) pools love them and have no problems, but some do.  [url=http://thepoolbiz.blogspot.com/]This blog[/url] has a biased view against salt systems, but it does document the kinds of problems that can occur.  It may be that the reason for more problems in some areas (as JohnRoss points out), especially Texas and Arizona in the U.S., is the use of absorbant hardscape materials such as limestone (and some flagstone) as well as hot dry summers with rapid evaporation.  In other areas, such as Florida, there are summer rains that would wash away (dilute) any splashed-out salt that would otherwise concentrate into some types of stone. Virtually all of the problems associated with SWG pools can be mitigated.  One can use less absorbant hardscape materials or can seal their natural stone (or even cement; we seal our simulated flagstone that is cement every year even though we don't have an SWG pool).  If one has an aluminum header for a vanishing automatic pool cover, then one can use a sacrificial magnesium anode to protect it (or a zinc anode to protect stainless steel and copper).  One can rinse patio furniture or diving board bases periodically to prevent salt build-up.  One can use (a small amount of) Cyanuric Acid (CYA) in indoor pools to reduce corrosion rates.  One can use curpo-nickel or titanium heat exchangers in their gas heaters or heat pumps instead of copper. Non-SWG pools don't use plain steel or zinc because of the corrosive nature of chlorine.  In a similar manner, increasing the conductivity of the water by adding extra salt requires some ramping up of the types of materials used, especially if they are already marginal.  Also, the increased chlorides alone may be an issue for stainless steel, aluminum and possibly copper as they interfere with the reformation of a passivity layer (see [url=http://www.epa.gov/triinter/lawsandregs/alloys/alloysreport.pdf]this PDF file[/url], for example). Richard

Dead pool water? Did they give you water chemistry test results or any explanation by what they meant by "dead"?  I can think of a few possibilities and solutions for them. One is that the pool was "let go" over the winter (i.e. not chlorinated).  Sometimes, soil bacteria get into the pool and consume the Cyanuric Acid (CYA) in the pool producing ammonia (technical info on this is [url=http://www.troublefreepool.com/degradation-of-cyanuric-acid-cya-t8880.html]here[/url]).  If this happens, then the pool appears to have an insatiable chlorine demand -- you keep adding chlorine, but get no Free Chlorine (FC) measurement.  For every 10 ppm CYA that bacteria consume, they produce 3 ppm ammonia and that takes about 24 ppm FC to get rid of.  Some of the ammonia can escape via other means (outgassing; consumption by algae) so to know if you've got ammonia in the pool you can buy an inexpensive ammonia test kit from a pet/fish/aquarium store.  It takes at least 8x the ammonia level as cumulatively added FC to get rid of it. Another possibility is that the Cyanuric Acid (CYA) level is very high, above 80 or 100 ppm, usually from continued use of stabilized chlorine (Trichlor tabs/pucks, Dichlor powder/granular) products.  This can also appear to be an unusual chlorine demand if there is a nascent algae bloom.  Unfortunately, for high CYA levels, the only way to lower them is via water dilution, so a partial drain/refill.  The long-term solution is to use a fixed amount of CYA and then use unstabilized chlorine (i.e. chlorinating liquid or bleach) which you can have automatically dosed using an automated dosing system such as [url=http://www.poolguy.fr/products/product-sanitization.htm]this one[/url] from the Pool Guy. Another possibility is that the Total Dissolved Solids (TDS) measurement is high, but this isn't a real problem since usually the TDS is just salt (sodium chloride) that has accumulated from chlorine usage. Richard

[quote user="teapot"]Hi Chem geek, So " The above links to BTU/sq.ft. data are with actual field measurements in strong Florida sun" heating a pool in summer when we don't really need it [:D] What we really need is the data for the above at the early and late season so we can work out if the swim season can be extended and at what cost.[/quote] The problem is that you can't easily "control" cloudy weather in a field test so that's why they use the full sun tests in the summer.  However, they DO additionaly measure the efficiency in simulated sun and shade conditions (with carefully measured light intensities) which is where they get the efficiency numbers in the spec sheets and you can use those to create the tables I gave and that does tell you, via efficiency, how much heat you can expect to get in different conditions.  It's a bit tricky to figure out, but if you look up your solar insolation typical for your area for the time of year you are interested in and apply the efficiency numbers, you can get a heat output. However, this won't tell you the heat loss from the pool and you need to know that to know if you can "keep up" with such loss.  So the above efficiency numbers are useful to tell you if the panels will be better than nothing and by how much, but it won't tell you what temperature you will be able to achieve in your pool, which of course depends on factors such as whether you use a pool cover.  [url=http://eosweb.larc.nasa.gov/sse/RETScreen/]This link[/url] will tell you the solar insolation anywhere in the world for anytime of year, but it's for a sunny day so is lower in the winter due to the sun being lower in the sky (passing through more air). The only reason I posted the real-world numbers is that sometimes people believe the laboratory efficiency numbers are just theoretical, but in reality they do translate to what happens in the field -- at least for amount of output for a given input (sunny vs. cloudy) and temperature difference (air vs. water).  It also had me figure out that the Navitron I used in my table as a basis for comparison was not the best choice (most efficient) of the evacuated tube technology. Richard

I just have those relatively inexpensive black flat mat panels so haven't even turned on the solar yet (though will do so soon) so my pool is only 52F (11C) [:(].  Our swim season doesn't usually start until around May, though I'll fire up the gas heat (plus solar heat first) to get the pool usable for April.  My wife uses the pool for swim therapy so it needs to be warmer at 86-88F (30-31C).

I have an update to the efficiency comparison of different panel types.  Actual panel efficiencies were measured for black flat mat panels for pool applications [url=http://www.fsec.ucf.edu/en/industry/testing/STcollectors/pool_ratings/index.htm]here[/url] and for flat glass-enclosed and evacuated tube panels for hot water [url=http://www.fsec.ucf.edu/en/industry/testing/STcollectors/hot_water_ratings/index.htm]here[/url] where the best black flat mat panels had around 1000-1060 BTU/sq.ft. while the best flat glass-enclosed panels were around 850-960 BTU/sq.ft. while the best evacuated tube panels were 650-740 BTU/sq.ft.  This makes the best case relative efficiency to black plastic mat panels: 100% to 91% to 70%. My original table at the start of this thread has implied relative efficiencies of 100% to 93% to 51%.  This difference is probably because the best evacuated tubes are better than the Navitron I used for the table.  A high efficiency tube from Sunda Solar with 739 BTU/sq.ft. is described [url=http://www.sundasolar.com/product_seido1%20series%20collector.html]here[/url] with a gross area efficiency of around 54% (compared to 41% for the Navitron) for a relative efficiency of 68% which is much more consistent.  The above links to BTU/sq.ft. data are with actual field measurements in strong Florida sun. Using the more efficient Sunda Solar as the evacuated tube example would change my table values in the 800 W/m2 case going from 54% to 42% while in the 300 W/m2 case it would go from 54% to 21%, so basically if you just add 13% to all values in the evacuated tube columns in my table, then you will get appropriate comparisons when using one of the best evacuated tube panels.  The main points in my charts that show how evacuated tubes get better when the temperature difference is larger, as with hot water heating and cold days, and also are better on cloudier days still applies as does the relative performance of the three panels. One should also keep in mind that practical considerations may make a situation where the evacuated tubes should do better than flat glass-enclosed actually turn out to be worse as described in [url=http://www.solarh2ot.com/images/Performance%20-%20Flat%20Plate%20vs%20Vacuum%20Tube.pdf]this report[/url].  The evacuated tube panels in this case are actually "too good" so they don't melt the frost/snow on the panels as quickly thus preventing as much heating as the flat glass-enclosed panel. Richard