CYA consumption, low chlorine?

[rporonga]

Hi,
I have a 20K gal pool with solar heater set at 87F, and I am using liquid chlorine. I see high consumption of CYA. The chlorine level sometimes falls to 0, but I easily bring it back to normal by adding more chlorine. So far, haven't had any algae problems, just a little cloudy water that clears up with more chlorine.
The issue is the CYA. My target is about 35ppm since I have a pool cover and the pool does not get much sun exposure. However, it keeps dropping. I add more from time to time, but now at the end of the summer it got to only 5ppm. I did not need to add much water since the cover prevents most of the evaporation, so it is not dilution by new water.
What mechanism leads to CYA consumption? And is it related to low chlorine?
I don't know if it matters, but I have a UV sanitizer.
I initially used liquid stabilizer from Leslie's, but after startup I have been using Clorox powder CYA from Walmart.

 

[mknauss]

How are you testing your pool water chemistry?
Elevated water temperature will accelerate CYA consumption.

CYA - Further Reading

www.troublefreepool.com

It is not possible to test CYA at levels below 20 ppm. So with your low level of CYA to start, a little loss will not allow for accurate testing.

 

[ajw22]

You UV sanitizer is consuming your chlorine causing you to require adding more chlorine to the pool then a normal pool without a UV sanitizer.

 

[rporonga]

I am having Leslies test it. They were consistently reading it between 30 ppm and dropping to 25ppm. But last time it tested 5ppm at 2 different stores in 2 consecutive days.

 

[JJ_Tex]

I am having Leslies test it. They were consistently reading it between 30 ppm and dropping to 25ppm. But last time it tested 5ppm at 2 different stores in 2 consecutive days.

I happened to be in Leslie's when you dropped it off and watched the guy test your water:

Seriously, Leslie's testing is terrible and don't put any faith in it. They may give you cool printouts with precise numbers, but it doesn't mean its accurate or consistent.

 

[ajw22]

I am having Leslies test it. They were consistently reading it between 30 ppm and dropping to 25ppm. But last time it tested 5ppm at 2 different stores in 2 consecutive days.

Get one good test kit - Taylor K-2006C or Test Kits and you can get accurate test results while stop running to all those Pool Stores.

 

[rporonga]

Get one good test kit - Taylor K-2006C or Test Kits and you can get accurate test results while stop running to all those Pool Stores.

I have a Taylor kit, but if I read the instructions correctly, the CYA test uses a lot of reagent, and I find it easier to have Leslies test it. So far, their CYA results made sense, I saw it go up by the expected amount when I added CYA.
Anyway, I was hoping to get some info on the mechanism that can lead to CYA getting consumed. Reading other posts regarding too high CYA level due to use of trychlor tabs, the only answer I saw was to partially drain the pool. If it gets consumed on its own, then one could just wait for it to go down.

 

[ajw22]

Read CYA - Further Reading

 

[JJ_Tex]

I have a Taylor kit, but if I read the instructions correctly, the CYA test uses a lot of reagent, and I find it easier to have Leslies test it. So far, their CYA results made sense, I saw it go up by the expected amount when I added CYA.
Anyway, I was hoping to get some info on the mechanism that can lead to CYA getting consumed. Reading other posts regarding too high CYA level due to use of trychlor tabs, the only answer I saw was to partially drain the pool. If it gets consumed on its own, then one could just wait for it to go down.

The consumption (really degradation of) CYA is very slow and hardly noticeable even at high water temps. I guarantee my water temp is a lot higher than yours in the peak of summer and I may notice a degradation of 10 PPM total over June-Sept.

I think you are assuming something is consuming CYA but it is just testing variance with Leslies. For $21 you can get a CYA test kit, or $13.50 for a large bottle of reagent. You probably spent that much on gas already, and you will know this is accurate and does not have a salesperson trying to sell you stuff every time you test.

Cyanuric Acid (CYA)

tftestkits.net

 

[AUSpool]

CyA will degrade but quit slowly.

CYA - Further Reading

www.troublefreepool.com