Where’d my CYA go????

[chris123]

First off, I’m one year into TFP after draining and refilling and it’s been a breeze. Following the advice of this forum has kept my pool beautiful and easy to maintain.

What I don’t understand is the sudden drop in CYA. Since the temperature shot up, with the pool now at 82 and the daytime temps over 100, I wasn’t too surprised to find the chlorine burning off more rapidly. But it has gotten to the point that something seemed off (dropping 2-3 per day and needing 2 gallons to maintain what I used to get with only 1 gallon) so I tested the CYA for the first time in many months.

I was shocked to find the CYA non-existent, less than 20 with the limitations of the dot test, and Leslie’s confirmed it was gone. It held 40-50 for the better part of a year now, and now it has disappeared. Luckily I stayed on top of the chlorine testing and I never let it go below 2. I’m now trying to recharge with liquid conditioner.

This phenomenon defies what I thought I knew about CYA from this forum, thinking it would stay in the pool forever unless I drained it out, and scaring me to death to ever use tabs again.

What became of the CYA????

 

[needsajet]

No worries, it's normal. Monthly testing is recommended, at least during the swim season.

There is loss via splashout and overflow. Some gets oxidised by chlorine, and there's other degradation pathways. Try a search on CYA degradation or CYA loss for some other info.

Great to hear that TFPC has been working for you It's nice reading a thread that starts out like yours does!

 

[chris123]

I knew of CYA loss through anything involving water leaving the pool, but not enough in my case to justify that. However I did search as suggested, and this thread was really enlightening:

Degradation of Cyanuric Acid (CYA))

So I took my CYA for granted after so many months. Initial monthly CYA test after test was consistent so eventually I kinda blew off testing for the last several months. When the heat kicked in I didn't expect the CYA to drop and reading through the thread I see now how it could be possible. I put in a gallon of liquid conditioner last night. Since I didn't need to worry about excess CYA, I stuffed my floater full of tabs so that I could save my precious liquid chlorine until the CYA gets back up to normal. Since the tabs didn't raise the FC immediately (dropped to 1.0 last night) I threw in a dichlor shock bag and by this morning I was back up to 5.0. I had to order more R-0013 so I won't be able to test for a few days.

Based on last summer, I don't expect the CYA to go down again this year. But for sure test monthly no matter what, and if it drops poolmath tells me dichlor/trichlor can bump the CYA up by 6-10 and drop the ph which is an added benefit right now.

Do I have this right? How long does it take liquid conditioner to stabilize before I determine that I should add more CYA or pull out the floater?

 

[needsajet]

Yep, you've got it. The liquid stabilizer will be in the water right away, and you can just use the calculation to know your level. Take a look at the bottom of PoolMath where it shows "Effects of Adding Chemicals". You can enter the weight or volume of any chemical there and it will tell you how much CYA you've added. You'll have to add the results for the liquid, plus the dichlor, plus however much of the pucks have dissolved. Your pool volume needs to be correct at the top for it to work. I would wait a few days before testing CYA.