Where's My Chlorine Going?? And How Do I Stop It?

[BikerBill]

Pool details (I can’t edit my signature for some reason and the data in the signature area is incorrect): 22.5 k gallon free form plaster/pebble pool, 1.5 HP Pentair WhisperFlo single speed pump, Pentair FNS DE filter, Aquacal Aerotemp 155 heat pump, 3” tabs or bleach used depending on CYA level. Taylor K2005 test kit for all test except CYA.

So I recently opened our pool to find it had no CYA according to a pool supply place. Last year when closing it the CYA was 77 ppm at the same pool store. I tend to believe the CYA disappeared over the winter and was close to zero because when I added shock the chlorine just disappeared within a few hours. I then added 4 lbs of CYA (should be equivalent to about 22 ppm) and it now tests at 42 ppm at the same pool store. I pre-dissolved the CYA granules in hot water by stirring (and stirring) them in a plastic pail so I believe the 42 ppm test result represents the added CYA.

Last night at dark I added enough shock to bring the chlorine level up to 10 ppm and checked it half an hour later. It only registered 2-3 ppm. New test reagent. This morning I tested it and it’s at zero. That would suggest organics are using up the chlorine. A similar test preformed earlier this week showed that the chlorine level held OK overnight, which would suggest just the opposite. I’m blowing through chlorine like there’s no tomorrow. I count 14 empty one gallon shock jugs (mix of 12.5% and 15%) and 3 empty 8.25% bleach jugs in my garage over 9 days and I have no chlorine in my pool.

Other test results: pH 7.4, TA 110, CH 210. Earlier this week the pool store measured total chlorine of 4.6/free chlorine of 0.4. Next day it was 3.6 and 0.0. That was before adding the CYA and before shocking to what should have been 25 ppm (I didn’t check the level). Yesterday they reported total chlorine of 0.8 and free of 0.3. When I test the water now I don't see much indication of combined chlorine.

I read that bacteria can eat up CYA. I also read that 1 ppm of chlorine should kill bacteria in one hour. So it seems like any bacteria should be long gone.

I should mention that the water itself looks quite good. Earlier this week there was some slight milkiness but that has disappeared.

At this point I’m really focused on getting chlorine to stay in the pool. Suggestions?

 

[AimeeH]

You read correctly that bacteria CAN consume the CYA and the result is ammonia which could be what your experiencing. If that is the case, that explains the very rapid consumption of the chloring you are adding. The answer essentially is to follow the SLAM process Pool School - SLAM - Shock Level And Maintain and continue adding chlorine until it begins to hold the chlorine.

 

[ajw22]

Your signature is too long. Shorten it as you edit it.

 

[BikerBill]

Is there a test to confirm the presence of ammonia? Is there some substance I can add that gets rid of ammonia?

 

[ajw22]

Is there a test to confirm the presence of ammonia? Is there some substance I can add that gets rid of ammonia?

Chlorine

 

[AimeeH]

+1^^^^^^



You CAN get an ammonia test from stores that deal with aquariums. I didn't suggest that because the remedy with or without it is the same. More chlorine.

 

[BikerBill]

Thanks, I see PetSmart sells them for $10. If I determine the ammonia level will that help me purchase the correct amount of chlorine I will need?

 

[AimeeH]

Thanks, I see PetSmart sells them for $10. If I determine the ammonia level will that help me purchase the correct amount of chlorine I will need?

I'm not sure we've dealt with the calculation of necessary chlorine to neutralize ammonia as an equation. It does happen that a bacteria can consume CYA and the biproduct is ammonia. Really......all that gets confusing and seems to dilute the fact that the answer is still chlorine. It's not that common but it DOES. Happen.

Knowing what I know, I'd keep adding chlorine and testing until I stopped seeing dramatic loss of chlorine. And the follow the SLAM process Pool School - SLAM - Shock Level And Maintain

 

[mknauss]

IF you did a test that accurately measured the amount of ammonia in your water, it will take 10X the ppm in added FC to eliminate the ammonia.

But - the remedy is the same. Chlorine.

To check and defeat it, if necessary, is to raise your FC in the water using liquid chlorine to 10 ppm using PoolMath. Circulate the pool for 30 minutes. Test FC. If 5 or below, raise your FC to 10 using LC, circulate for 30 minutes, repeat until your FC is above 5 ppm after the 30 minute circulation.

Take care.

 

[BikerBill]

SLAM Update & Where Do I Go From Here??

I've rigorously followed the SLAM instructions and have been SLAMMING away for four days. I've maintained the free chlorine level in the upper teens based on a CYA level of 40 ppm. Combined chlorine has fallen from 1.5 ppm to about 0.25 ppm. Overnight free chlorine loss is 1.5 ppm. Day time free chlorine loss is 5-6 ppm depending on sun and cloud levels. The water is nice and clear as it has been throughout this episode. But things don't seem to be getting any better. I just seem to be stuck with a too-high chlorine demand.

What can I try next?

 

[kellyfair]

Are you still relying on pool store testing for CYA? If so, You really need to be able to test your CYA yourself.

 

[Mendy48]

Re: SLAM Update & Where Do I Go From Here??

CC at 0.25....interesting.... are you testing these levels yourself? What type of test kit do you have?

I've rigorously followed the SLAM instructions and have been SLAMMING away for four days. I've maintained the free chlorine level in the upper teens based on a CYA level of 40 ppm. Combined chlorine has fallen from 1.5 ppm to about 0.25 ppm. Overnight free chlorine loss is 1.5 ppm. Day time free chlorine loss is 5-6 ppm depending on sun and cloud levels. The water is nice and clear as it has been throughout this episode. But things don't seem to be getting any better. I just seem to be stuck with a too-high chlorine demand.

What can I try next?

 

[kellyfair]

Re: SLAM Update & Where Do I Go From Here??

CC at 0.25....interesting.... are you testing these levels yourself? What type of test kit do you have?

Siggy has Taylor 2005...

 

[Mendy48]

Re: SLAM Update & Where Do I Go From Here??

Got it.. wasn't sure.

Siggy has Taylor 2005...

 

[BikerBill]

I have a Taylor K2005 test kit, which does not contain a FAS-DPD test. None of my local pool places stock a FAS-DPD only test kit (Taylor T-1515-A). I couldn't see buying a K2006 or TFT-100 test kit since it would duplicate so many of the tests I already have. I realized that if I just bought the reagents (R-0870 and R-0871) and used the measuring block and the R-0003 from my K2005 kit I'd be in business. So that is what I did. So all my FC and CC readings have been made using the FAS-DPD method.

Yes, my CYA results are from a pool place. I tested CYA using my K2005 kit years ago and remember thinking it seemed kind of Mickey Mouse. The pool place has an automated spin sample test system. I can't vouch for it's accuracy but the repeatability is very good. I can try testing CYA with my K2005 and see what I get.

Last night I had no free chlorine loss overnight (first time!). Today was brilliantly sunny and I lost 7.5 ppm free chlorine from 8:00 AM to 3:45 PM. So it seems like whatever amount of CYA I actually have is not adequate to keep the chlorine from being burned off by the sun. I'm reluctant to add more CYA since I was hoping to use the 3" pucks this summer for a few months and wanted the CYA to creep up slowly.