CYA High and Rising

[Murray1723]

I have 41,500 gallon gunite freshwater pool sanitized by chlorine and ozone. My CYA level on 5/19/23 was 137. I quit using stabilized chlorine tabs and instead used a cup of Poolife Turboshock every few days for chlorine. On 6/30 the CYA was 165 and today on 7/6 it’s 184! What could be causing it to continue rising when I haven’t used stabilized tabs since May? I have a motorized cover that sits in a well, so we lose a fair amount of pool water into the well that gets replaced with city water by an auto-feeder.

 

[mknauss]

Welcome to the forum!
How are you testing your pool water chemistry?
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[Murray1723]

I’m taking a sample to a reputable local pool supply store (same one each time). I reached out to my pool builder and he said don’t worry about CYA even in 200-300 range as long as the water is clear and easy to manage. He said city water can contain CYA. Use non-stabilized tabs in the skimmers and let rain water into the pool and it will be fine.

 

[mknauss]

He said city water can contain CYA.

Oh my. That is so false. I would not trust information from that source.

Sorry - but that is all so false. Please read through Pool School that I linked.

 

[duraleigh]

That points out something we hear about on this forum frequently. Good Pool Builders with absolute ignorance about pool water chemistry.

 

[Mdragger88]

Sorry to tell you but aside from your outrageous cya level (if it can be trusted) making it pretty impossible to keep a sanitary pool
FC/CYA Levels
.... "Min FC" is 7.5% of the CYA level
.... "Target FC" is 11.5% of the CYA level
.... "Shock FC" is 40% of the CYA level
you are also likely sorely under chlorinating.
Here’s what that cup of cal hypo does:

The average residential pool uses 2-4 ppm of fc daily give or take depending upon conditions.

You have a very large pool which is a substantial investment. You need a proper test kit to take care of your investment & keep it sanitary .
Test Kits Compared
Clear doesn’t automatically equal sanitary.
You shouldn’t make any adjustments based on the pool store tests.
When you get a k2006 or tf100/pro in do all the tests & post the results so we can help you get back on track.

 

[Murray1723]

Back to my original question of how CYA can be increasing when I’m not adding stabilized tabs, any theories other than city water, or should I not assume the test results are correct unless I do them myself?

 

[mknauss]

or should I not assume the test results are correct unless I do them myself?

Bingo. Test error. If you are not physically adding CYA (stabilizer, trichlor, or dichlor), then it is not able to increase in your pool water.

 

[Mdragger88]

or should I not assume the test results are correct unless I do them myself?

This
The cya test is the one they get wrong the most!