MILKY PALE GREEN WATER

[roger888]

Since successfully emptying my filter of sand and replacing it with zeolite, I've been trying to get the pool cleaned up and ready to go. The water temperature here is 18 degrees, and it won't be long before we want to be in it. My problem is that the water stubbornly refuses to budge from a milky pale green colour.

It's an in-ground pool, irregular shape but volume approximately 80-100 cu m. So far, I've got most of the muck out with net, vacuum brush etc. It's a bit difficult to tell how much is left because I can't see the bottom. I've been filtering 8 hours or so each day for more than a week. The pump is a Hayward SP1622 powered by a Hanning 1250w motor. From what I can find (these models are obsolete) that's about a 1.5hp pump, with a design flow rate of a bit less than 20 cu m/hour. I should be getting total turnover in about 4-5 hours.

The water seems pretty clean, but a pint glass sample reveals some very fine floating particulate matter. I've shocked twice, once with 5 litres eau de javel, once with commercial stabilised chlor choc to get some stabiliser into the water. But the water remains a milky pale green colour.

At this stage, I'm not focussing on getting the sanitation right. I simply want to get the water clean and clear before I start putting other chemicals in. (At the back of my mind also is that if I need to empty and refill, I particularly don't want to have wasted time and money putting chemicals in.)

Readings taken today, 4 or 5 hours after shocking:

TDS: 331 according to my Hach electronic meter, 0-500 according to Aquachek strips

Total chlorine: 1 (Aquachek)

Free chlorine: 0.5 Aquachek, 0.75 Aquachek Trutest

PH: very variable results. 7.1 and high error on two Trutest readings, 6.2 on Aquachek strips

Total alkalinity: again variable. 52 and 239 Trutest, 40 Aquachek strips

Cyanuric acid: 0-30 Aquachek strips

In each case, I've taken two readings within a few minutes of each other. The TDS, chlorine and cyanuric acid are to be expected, given what I've done so far. I don't understand the high variation on PH and TA.

One possible clue. I've read that excess copper can turn water green. The previous owner was obviously in the habit of using copper sulphate for algae control, because he left me the (very small) remains of a 3kg tub of Blue Crystal copper sulphate. So at least 2.5 kg has been chucked in the water over the last few years, possibly more. But I don't want to jump to conclusions if there's a simpler explanation.

An alternative possible clue. It's a concrete pool (I assume). The walls and floor are painted white. A stiff brush on the walls pulls off milky paint colour. Am I simply seeing fine paint powder clouding the water?

Any advice? Keep filtering? Is there a simple test for excess copper, or should I get the water tested? If it's paint, do I need to drain and repaint? What with? All comments and guidance welcomed by a novice!

[Théière]

Ok Roger, your going in the right direction but probably have some way to go. Thank you for publishing the test results that is very useful especially showing the variance between test strips and the truetest meter.

Firstly don't worry about TDS it is not really important.

The fact that it is a milky green shows that you are killing the algae which will go a milky grey when actually dead. The fact that green is still present shows that the algae is still alive and multiplying. brushing of the walls of the pool and removal of as much dirt as you can are vital parts of the getting controll of your pool.

Shocking a pool is not the addition of shock but a process where you raise the free chlorine level to 5-10ppm and hold it at that level with very regular additions of chlorine untill the algae and or anything else is dead. As you added 5 litres of  bleach (what strength?) that should have taken the chlorine level to near 10ppm but it gets used up very quickly killing and oxidising the algae so after 8 hours the level could easily be down to only a couple of ppm.  You need to add 5 litres of bleach aroung 12% as often as required to maintain the shock level at around 10ppm until it stops dropping. Cheapest version if you are not already using it is the 12% javel biddons sold by brico's at around 18 euros for 20 litres and you may well need two of them.

I am concerned at the potential copper problem, yes you can get a test for this something like the la motte test or the latest Lovibond or Palintest, do not bother with the dip strips for copper as I have been unable to work out what the level was using them. If there is copper present in the water I would be surpised as it is one of the few additions that actually prevents algae forming as it can actually kill it.  That said I would never use copper additions in a concrete, plaster or tiled pool as copper staining is a real problem. Copper can be used with care in a vinyl liner pool however using the correct chlorine level at all times prevents algae and does not stain.

Regarding the PH, it maybe worth getting a standard drop tester from a shop as the variance is so wide. As you have a concrete pool then the low PH will strip some of the surface so try to get the PH back up to 7.4, please note once the pool has been shocked this can through up a high reading for PH but not at the low level you currently have. Keep filtering, personally I would filter continually until the water clears.

That's probably enough for now but there will be more you need to do in order to care for your pool long term but one step at a time. 

[roger888]

Hi

That's very helpful. Thanks.

Yes, I'm using 20 litre eau de javel bidons from the brico, 9.6% disponsible chlor.

The main message I take is that shocking requires not only elevation to 10ppm Cl, but sustaining it at that level. The fact that my Cl level drops rapidly is presumably not just to solar burn off but to the fact that it's still oxidising residual algae/bacteria/muck. And hence the water's going pale milky green. (Update: she who has better colour vision than I says the colour is eau de nil).

The point about Cu is well made. If I had high Cu, there'd be no algae/no green. So ignore for now.

Hence next steps: More Cl in the morning, filter filter. Measure Cl. Probably more Cl next day etc etc. Keep Cl at 10ppm. etc

I'll let you know how I get on.

[Théière]

No problem Roger, it's actually better to add chlorine in the evening as you don't suffer UV burn off and algae don't breed as fast over night.

 

[Poolguy]

John

I think that we should also ensure that Roger's Cyanuric Acid is above 30ppm as the tests were not conclusive on that.

In addition, I am not convinced that the TAC is Over 100, and that will cloud the pool water for sure and make nonsense of all the rest besides. So add bi carbonate soda till you get a Clear 100+ reading on Total Alkalinity (TAC).  Its will send the pH through the roof but do nothing about that till the Bi carb has completely dissolved - takes about 2 days to be sure you've got a reliable result.

So then you've got the basic balance and your Chlor choc is (as John says) doing the killing business. All the algae is dead an lying on the pool floor after you've turned off your pump for the night.

I hope that you have given the Zeolite 3 good Backwashes and 3 good rinses alternatively to both wash out the dust and arrange the particle sizes in the filter.

Then it'll be a matter of vacuuming the residue to waist and you should be away.

Andrew

[Théière]

I agree Andrew but as the test results are so varied its difficult to give very clear advice hence my concentrating on killing the algae.

Bottom line is to spend some money on a good tester either one of your scuba+'s or the Minidirect photometers as even the pool shops use dip strips these days. 

[roger888]

Thanks for the comments and advice. Much appreciated. The situation is improving, but slowly.

To answer your various questions:

On TA, my Aquachek is consistently showing high levels. The last nine are high error, high error, high error, 127, high error, high error, 189, 159, 157. Having said that, my Aquatest test strip today showed ~80. I should add that all test strips are fresh and within date (November 2011). I have to say that if there is this wide variation in readings between different test methods using strips then it really does seem to make sense to invest in better equipment.

Incidentally, I noticed while playing around that simply holding my thumb over the Aquachek lamp gave a Cl reading of 2.0. Green fingers? In another test, I dipped an Aquachek strip as directed, and got a reading of 7.8. I then re-dipped the same strip, and got a reading of 10.0 off it. How reliable are these strips and meters supposed to be? There seems to be far too much variation for effective calibration.

Andrew: yes, the zeolite was well backwashed and rinsed after filling. It's been done again a few times as pressure rose after filtering muck out of the pool.

The water is now beginning to hold chlorine, despite low CYA. Approx 8 hours after another 5 litres of javel, and a day of hot sunshine, I still had 1.8ppm. Ph is also high, but I'm not worrying about that at the moment.

Having said all that, I have realised today that there is still more muck and organic matter on the floor of the pool (which, if you remember, I still can't see) than I thought. The surface appearance is clean and turquoise, but I suspect that lurking beneath is a different matter. In the circumstances, I am going to suspend Cl choc for a while, and concentrate on physical methods of muck removal. It doesn't seem to make sense to keep chucking in javel to oxidise stuff which should be removed first.

I'll keep you posted.

[Poolguy]

Roger

'Incidentally, I noticed while playing around that simply holding my thumb over the Aquachek lamp gave a Cl reading of 2.0. Green fingers? In another test, I dipped an Aquachek strip as directed, and got a reading of 7.8. I then re-dipped the same strip, and got a reading of 10.0 off it. How reliable are these strips and meters supposed to be? There seems to be far too much variation for effective calibration'. Ed Roger

I think that you have answered your own question. I will only recommend a photometer method using pastilles as it has been proven to me too many times that other methods of testing leave too much error in decision making- and this stuff is too important to be guess work, its the health of bathers after all which is not at all the trivial affair that some pool owner's think it is.

I would never recommend Aquacheck as a consequence of the above.

If oyu TA is high (above 150) and you ph is normal (7.2 - 7.6) then your calcium hardness will be low bring all the calcium out of solution to settle on the pool bottom. So let your pool rest for a time to see if you get settlement.

Andrew

 

 

 

 

[Théière]

Roger,

I can only agree with Andrew, A vinyl liner pool is relatively easy to look after,  a concrete, plaster or tiled pool requires more knowledge and the basis of that has got to be accurate testing.

I know you have your hands full at the moment but you have a fair bit to learn with regard to balancing your water properly to avoid the problems of cloudy water and wild PH variations etc

If the budget allows invest in a good tester as it will almost certainly pay for itself in reduced chemical additions runs to pool shops etc.