Help with My CYA Levels

I’m a first-year pool owner here, and thanks to this forum, I’m pretty familiar with pool chemistry now. The one thing I can’t seem to get a handle on is CYA.

I took over this pool in April 2024, and our Taylor K2006 test kit has been showing CYA readings of 175+, even with a dilution test. We figured the previous owners must have over-stabilized it with tri-chlor tabs or shocked it heavily to sell the house.

I understand that CYA doesn’t lower naturally, and draining/refilling is the only way to reduce it. I’ve done small drain/refills about 7-8 times, draining roughly 2 feet each time. We live in North Texas, so with the heat, I also add water 1-2 times a week. Despite all this, my CYA is still reading 150+.

Wouldn’t all the drain/refills have impacted my CYA by now? Does topping off the pool count as “diluting” it, or does CYA remain the same regardless? The only chemicals I’ve added this year are liquid chlorine, Cal-Hypo shock, muriatic acid, and baking soda.

I’m feeling a bit lost with this CYA situation. Any tips or advice would be greatly appreciated!

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If the CYA level is 175, you’ll need to completely drain and refill the pool. When restarting, be sure to add the correct amount of stabilizer (also known as cyanuric acid).

CYA doesn’t break down due to sunlight or splashing. You’d have to backwash a lot every day to see any noticeable decrease in CYA levels.

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I recommend having your water tested at a different facility or having someone with expertise in the test verify it for you. It’s the only subjective test in Taylor’s kit, so if your water isn’t perfectly clear, any cloudiness can lead to an inaccurate high reading. Additionally, test results can be influenced by temperature; it’s best to conduct the test between 75° and 80°.

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To effectively reduce your CYA levels, draining the pool is essentially the only solution. Other factors like evaporation and daily pool use have minimal impact on reducing CYA.

For instance, if your CYA level is at 200, draining 50% of the water and refilling should bring it down to around 100. Draining 75% would lower it to about 50, and so on.

As a first-time pool owner myself, I used pucks to bring my CYA level to a suitable range (30-60). Now, I only use one or two pucks for maintaining chlorine and CYA. Once my CYA reaches 60, I’ll stop using the pucks.

Also, ensure that any products you use do not contain CYA!

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I’m not sure whether you’re draining from the top or bottom, but it should be done from the bottom.

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Been there, done that! I’ve been a pool owner for two years now, and here’s what I’ve learned from local pool experts and hands-on experience: Use the backwash feature of your system to drain water from the top level where the CYA (cyanuric acid) accumulates. Continue backwashing until your skimmers are nearly dry, then refill the pool. Test the water after each backwash to gauge how many cycles you need. I reduced, but did not eliminate, the use of chlorine tablets since CYA originates from them. Instead, rely more on shock treatments rather than tablets to maintain pool health.

I haven’t verified this with a second source, but it definitely resolved my issue.