Where's my CYA

[joshhighley]

Opened my pool yesterday morning and started testing. ph 7.2. CYA was 0, which I've not had before --usually there's at least some when I open in the spring. I added 5 lbs of dry stabilizer via skimmer sock. CYA should have at least been 20 , and my CYA test showed some cloudiness but was still well below 20. I took a sample to a pool store this morning to confirm and they tested it at 5.

Where could my CYA be going?

My water temp is 60F, would that impact it that much? I let my sample warm up before testing.

18x36 w/ deep end, about 30,000 gallons, vinyl

 

[mknauss]

Stop. Have you tested your full chemistry? Please post a full set of test results. What does the water look like?

When one shows a complete loss of CYA over winter, ammonia can be an issue. Adding more CYA just feeds the bacteria that makes the ammonia.

Let us know the answers to the questions above and we can provide guidance going forward.

 

[Oly]

Trust your test kit results and calculate how much CYA it takes to raise your levels by 10ppm.
Dissolve in 10ppm worth, wait a day or two and retest. You can buy an inexpensive16oz bottle of reagent so testing often is not an issue. It is stable and stores well too. CYA degrades in my pool as well over the winter and also in my hot spa water but it does not drop to zero so heed Marty's advice.

 

[joshhighley]

TA was 30, I've since added about 20lbs of baking soda but haven't re-tested. FC was 7 this morning (confirmed by pool store, FWIW), down from 10 last night. Pool is green from algae. It was mainly on the bottom after opening but I brushed everything to stir it up.

I pump my pool down to below the returns for winter, so I always have to add some CYA. I've never had it at 0 when opening, nor have the tests not reflect what I've added

I've been doing TFP for 3 years now with no issues. TF100 test kit. This is the first time I've been to a pool store, but wanted some kind of second opinion on my test results.

I added some algeacide when closing last fall to see if it would make a difference when opening -- that's the first time I've used it. I also added 55lbs of boric acid last spring. Other than that, just typical TFP chemicals as needed: baking soda, borax, muriatic acid, and liquid chorine.

 

[zea3]

Keep in mind there is a plus/minus 10ppm margin of error in the CYA test, and it is difficult to measure below 20 ppm. I would add enough for an additional 10 ppm via the sock method then re-test. Since you did hold some chlorine overnight I don't think ammonia is your problem. Do you know what your CYA level was at closing?

 

[joshhighley]

CYA at closing was probably around 40. I added 5lbs of cya granules yesterday that should have put my cya around 20

Retested TA: 90. ph is 7.5

 

[joshhighley]

Pool is now holding CYA at about 20. From reading about CYA->ammonia, I suspect that was my issue initially. It seemed to use a lot of chlorine at first, but I assumed it was the algae.

Pool is still blue-green though and doesn't seem to be clearing. Not a lot of FC use and I'm holding it at 10 - 12. CC < 1. I'm running my pump 24x7.

 

[zea3]

What kind of filter do you have, how big is it, and how big is your pool?

 

[joshhighley]

What kind of filter do you have, how big is it, and how big is your pool?

Pool is IG vinyl 18 x 36 with a deep end, a bit under 30,000 gallons. Filter is sand, 300lbs I believe. The pool is only 3 years old, been doing TFP since the beginning.

 

[zea3]

I would say your filter is a little small for the size of your pool. Sand filters also take longer to clear the dead algae out of the pool. This is when POP (pool owner patience) is needed. Take a photo at the same spot and time everyday and you should be able to note the subtle progress day by day. Use pool steps or a manual pool vacuum as a reference point.