Green and now blue!

[JohnRoss]

In the past we have had the odd bit of green in one or two places in the pool but never like this year. The water was all green and after much filtering with a 6 micron bag and chlore choc several times plus 5 litres of javel 9.6% the green has gone and the water is now clear apart from being a slight blue colour. A bit like a dilute copper sulphate solution. The filter bag comes out clear of the green slime now.

The pool is a salt water Desjoyaux pool, 75 cubic metres approx, with an electrolytic cell to produce chlorine and I am wondering if some combination of the chemicals in it is giving this blue colour. Did try some Pro Azur floculant at one point but all that did is clog up the filter bag. Any thoughts folks........JR

[Théière]

It may be a bit boring but have you got a full set of test results?

I reckon I could tell any salt chlorinated pools at 25m distance by the slightly turbid grey/green hue. Comparing this with a direct chlorine dosed pool they have a much clearer blue sparkle to them. I think your direct javel usage has shown what Poolguy and I have been rambling on about for some time but you have just discovered a properly shocked clean pool.  That said I have seen some recent salt chlorinated pools using newer units at the correct levels and they looked better than the original salt pools I was called in to look at.

[Gemonimo]

My salt unit is finally giving up the ghost and I have to treat the water with chlore a couple of times a week and the water has never been clearer.  My pool guy who opens and closes the pool every year has suggested that rather than invest mega bucks in a new salt water treatment, he'll just remove the old one and I'll continue with chlore.  I don't know why I had the salt water system in the first place. I'm obviously a salesman's dream[:D] 

[Théière]

No Gem, I don't think you are a salesman's dream. There is a cost to trundle off to the brico's for eau de javel and hydrochloric acid, both in time and fuel. comparing that cost with the cost of a reasonable salt chlorinator over 5 years probably about the same (obviously dependant on where you are compared to the shops). You also don't have to handle chemicals which are usually heavy to move and lets face it you have to take some care with using.

Now you say your salt unit is dead, is that just the salt cell which does have a finite life but replacement cells can be purchased or the power supply unit in which case R.I.P.

I have done some experiments with low cost chemical dosing units so people can stop using multi action galets (Osie I haven't forgotten) and the results were good and required minimal manual intervention (dependant on budget)

 

[Gemonimo]

[quote user="Théière"]Now you say your salt unit is dead, is that just the salt cell which does have a finite life but replacement cells can be purchased or the power supply unit in which case R.I.P.[/quote]

How can you tell the difference? The lights on the unit function but the light for 'service' remains on all the time and the level of salt never diminishes. My PG opens the pool in the spring, treats it leaving the water ready for use so in theory I don't have to schlepp to brico or anywhere else.... he does it[Www] In the autumn he half empties it, fills it with whatever and covers it. The salt unit is just something else to go wrong.

[Théière]

You need a bright spark to measure the output to the salt cell, if that's good then a replacement salt cell is all you may need. The cheapest cells use a mesh type plate with very thin titanium coating, more expensive use flat metal plates with thicker titanium coating hence longer life. In older units they don't always self clean, newer ones generally do so if your pool guy doesn't clean the cell it may just be caked up (look for calcium deposits on the plates).

With your now failed salt chlorinator (possibly), you may need to do more schlepping [:)]

[JohnRoss]

Ok did a very crude experiment this morning. Crushed a floculant tablet and put a little into an empty plastic water bottle and agitated and waited. Over the next 30 minutes the water took on a light blue tinge. I then added a little bit of a chlore choc tablet but no significant change. I then introduced a small quantity of diluted javel 9.6 solution and immediately the water in the bottle turned a nice shade of green. A bit later on I added a small quantity of salt but no further change. Finally I sprayed the remaining crushed floculant tablet with the diluted javel and immediately a bright green colour was produced.

This proves very little except that combinations of pool chemicals can change the colour of the water. I suspect that the floculant may have some added blue colouring. The javel and floculant reaction was not responsible for the colour of the water in the pool as the green was in evidence before I added the 5 litres of javel and indeed before I added the floculant. The blue tinge to the water in the pool that I have now was only visible after several days of filtering and several days after pouring in the javel. The blue tinge is clearly a result of a chemical, probably the floculant, and not a reflection of the sky as the depth of colour is constant regardless of the lighting conditions. I accept that the experiment with the bottle was not representative of the balance and amounts of chemicals in the pool however an interesting result!...............JR

[Théière]

Still wondering why you have flocculent with your Desy pool, have you changed the filtration?

Chlor choc is rapidly dissolving chlorine with cyanic acid, eau de javel is chlorine bleach so there shouldn't have been any significant change between the two just the concentration from the two additions. Most floc is alum based so the colour wouldn't really be an issue unless there is as you say some copper sulphate (algecide) added for extra umph. copper has many colours from blue to green and muddy browns usually dependant on the chloride compounds formed and the Ph. Adding extra chlorine would take the Ph above 8.3 at which point copper drops out of suspension...

[JohnRoss]

No the flocculent or floculant, to use the French spelling, was added just as an experiment and only about a third of the amount recommended for a pool of this size. It did clog up the filter bag as you might expect so not that much would have got into the pool. Easily washed out by blasting with a hose. Any that did settle on the bottom seems to have been sucked up by the robot.

I checked the chlorine level some hours after adding the javel and the reading was very high, off the scale in fact on the tester I am using. i.e. above 5. The ph was high also, about 8.4, so I suspect what you say about copper might be the case. I notice also that there are some small bits of blue stuff showing on the surface of the floculant tablets. The water temperature is about 30 degrees just now as I have been running the solar heating pipes. I guess chemical reactions might be a function of water temperature too.

I will check the levels again later and if still high I will turn down the control on the electrolytic cell psu as it is on 80% just now. i.e. on for 80% of the time and off for 20% of the time................JR

PS I montor the current flowing in the electrolytic cell, just a touch over 10 amps, a tad high maybe and is a function of how much salt I put in to top up in the Spring.

[Théière]

Try diluting your sample before testing to give you an idea of the chlorine level then multiply the result by the dilution ratio.

[osie]

Re: salt chlorinator...

I had a salt chlorinator that stopped working and was happy to just get shot of it and start adding chlorine.  No one could say for sure what exactly was wrong but it ended up possibly spending a fortune to find out.  As electrical diagnosis was not my forte.. putting chlor in the pool was the preferred choice.

[Saucedecochon]

Firstly I notice you are talking about a 30 degrees water temp. Thats approaching danger temperature for algae as far as I'm concerned. Your pH seems all out of kilter too, and as it's pH level which is kind of important, if all the other pool mechanisms and chemicals are going to perform to spec I would get that right 1st.

 Run on chlor for a day and if your cellule is removable, take it to your local dealer, or who you got it from, and ask them to run a test. That'll establish which is at fault, cellule or coffret.

You may have overcooked the pool temperature for the max output of an electrolysis cell.

 Losing some contaminated water and replacing with fresh tap water, as much as you can stand financially always helps with pH.

 Flocculation should be done before you filter and pump to waste, as the algae might look dead but theres always a few little b*****s hang about to start multiplying again. Not sure what your test was about.

Did you say what level of saline the solution is?? Presume you have enough salt ppm?Hit the new water with a chlor choc to bolster the electrolysis effect after you've added salt if its in deficit.

I'm never at my gaff at the right time so mine goes green for a habit, but I can normally turn it round in 4 days.

If any of this makes any sense or helps, or if you want a chat, pm and I'll bung you my fon number.

[Saucedecochon]

I just noticed you say you are running at 80% and an incredibly low 20%.

If your water temperature and pH are that far out, your cell has no hope at 20%, and may struggle at 80%.  I always run mine in high summer at 95% - !00%

[Théière]

It is absolutely normal to have pool water around 30 deg at this time of year and providing there is sufficient chlorine available to deal with any algae then there is no problem. It is true that you may get through more chlorine at a higher water temperature and losses to UV will be greater with strong sunlight so cyanuric acid levels around 30-50ppm are advisable although several SWG manuals advise slightly higher so follow the manual.  There is no need to replace any water unless the cyanuric acid level is too high 80+ ppm. Replacing water when the evaporation is so high anyway in July is not needed and also with the water restrictions currently in place in many regions is not allowed.

The Ph is only high as the pool is currently (was) being shocked and as chlorine has a Ph around 11 then readings will always show high and this is generally ignored as it is a temporary situation, as the chlorine is used up the Ph will return to normal levels. Adjusting the Ph down now will also lower the alkalinity and require the Ph to be increased immediately following the shock treatment or erosion of pool surfaces and equipment may occur together with increasing the alkalinity so a complete waste of time and chemicals.

It is the chlorine level in ppm relative to the cyanuric acid level which is the important factor and not running at 80 or 100%. Not sure about taking advice from someone who's pool "goes green for a habit" [blink]

The OP (JohnRoss) question was where did the blue water come from.

[JohnRoss]

Well we have had a lot of rain over the last few days and the pool water level has come up quite a bit. The Chlorine measures about 4 now so it has dropped and the pH likewise, now measures 7.2. The water has lost quite a lot of the blue colour so hopefully all is now well......JR

PS I have not run the electrolytic cell at all for the last couple of days.

[Saucedecochon]

Just noticed the "response". Yes teapot, all very true and scientific.

However beware of part quotations. Full sentence was " Since I am never down at the right time, mine goes green for a habit."

I largely live in the UK, and so cannot adjust and test on a daily basis once the pool is opened up.When I am in France the pool has never turned green.

Sadly, deity that I am, controlling rainfall, wind, sunlight, evaporation, leaf and animal ingress, power interruptions,etc etc are only just beyond my limit even on site, let alone at 1000 miles distance.

[Théière]

Yes Saucy I understand your absence, short of a lottery win I am in the same position but mine stays crystal clear and algae free, I have direct chemical dosing but you have a salt water chlorinator so it still shouldn't go green if things are all working correctly. I have been down on salt water chlorination as I have to sort out more pools with them than other types but with petrol prices and time etc together with better power supply units these things do have a place for domestic pools. I therefore deduced that something in your pool is not working as it should, testing the water accurately (not using dip strips) is half the battle as adjustments can then be accurately. I would be out of business if they all ran perfectly [:)]