Hmmm...CYA issues (?)

[LizC]

Hello,

I came to this website a month ago after growing algae for the first time. I think I successfully shocked my pool with info on here at that time despite a CYA level of 85 or 90. Yes, I had to use A LOT of bleach but it solved my problem so it was worth it to me. I stopped using my tri-chlor tablets at that time to keep CYA from raising even more and switched to liquid bleach.

My pool has looked crystal clear all summer (even despite the algae) but now my pool is cloudy and here are my readings:
CYA - 0 (how is this even possible?)
FC - .4
CC - 3.4
TA - 180
CH - 230

I put a box of borax in a little while ago in hopes to raise the pH a bit. I also filled up my feeder with tri-chlor pucks again since I need both stabilizer and chlorine. What should I do now?
How is it possible that CYA can drop that much? I had just checked it last week and it was still at 85.

Thanks so much for any advise!

 

[Isaac-1]

How did you check it?

 

[LizC]

I have a Taylor FAS-DPD 2006. I bought it at the end of 2011 but I did just have to buy some new reagents. The chlorine and cyanuric acid reagents are new this year.

 

[Isaac-1]

In that case do you have an auto fill that may be hiding a below ground pool leak?

 

[PridgNYC]

Did you do any drain/refils to reduce your CYA level? Because the only other thing that could reduce your CYA level that fast would be a fast leak and an auto refill system.

 

[JamesW]

I would suspect test error first. Double-check the test result to confirm. If you do confirm 0 CYA, then I would next suspect that you had a bacteria get in your pool, and convert your CYA to ammonia.

it-can-happen-to-anyone-zero-chlorine-cya-ammonia-t10974.html

Note that the sudden high cc level suggests the bacteria hypothesis unless it can be explained some other way.

 

[LizC]

Thanks so much for the info. I don't think I have user error. I double checked with my test strips too and it confirms 0 CYA and I had 85 last week. Assuming it is the bacteria, what would you do?

I put in 2 pounds of stabilizer this morning and still have tri-chlor in the feeder. I don't want my CYA to get back up to 85. Should I add more stabilizer or wait a week and retest the CYA to see? Should I assume a CYA number of 30 or 40 and start to shock the pool? Or should I wait until I actually know my CYA level in a week?

Thanks again

 

[LizC]

I forgot to mention that I don't have an autofill pool. I haven't added any water since opening in May.

 

[Richard320]

Thanks so much for the info. I don't think I have user error. I double checked with my test strips too and it confirms 0 CYA and I had 85 last week. Assuming it is the bacteria, what would you do?

I put in 2 pounds of stabilizer this morning and still have tri-chlor in the feeder. I don't want my CYA to get back up to 85. Should I add more stabilizer or wait a week and retest the CYA to see? Should I assume a CYA number of 30 or 40 and start to shock the pool? Or should I wait until I actually know my CYA level in a week?

Thanks again

Assume it's there and target FC accordingly. If it did break down the CYA that was in there, you'll have ammonia in there, and it will take a whole lot of bleach to neutralize it before it can even start killing algae.

 

[LizC]

Great, thanks!

Heres my progress:

At 10:30am I added 5-121 oz of 8.25% bleach, apparently that wasn't even close to enough.
At 11:30am FC was .4 and CC now at 6.0
I added 7 more things of bleach just now. I only have 3 left so I better make a trip to the store soon.

 

[JamesW]

This might take quite a bit of bleach (maybe as much as 50 to 75 gallons). Just keep following the shock process as long as it takes. You might want to stock up on FAS-DPD reagents if you don't have a lot.

You might even want to consider doing a partial drain and refill to get rid of some of the ammonia.