CYA too high

[rmozer]

My CYA level (>90) appears to be interfering with my algae control.
I understand that to reduce my CYA level, I have to pump down my pool and add fresh water.
Can someone provide guidance on how much old water to remove and replace?
My pool is 16 x 32 and has about 21,000 gallons.

Thanks
Bob

 

[CrystalRiver]

Is it for sure below 100?

To get from 90 to 30, you need to replace two thirds of your water. Aim to replace at least that much - it's a lot easier to add CYA back in if you went a bit too far, than have to deal with not getting the result you wanted.

 

[rmozer]

Is it for sure below 100?

To get from 90 to 30, you need to replace two thirds of your water. Aim to replace at least that much - it's a lot easier to add CYA back in if you went a bit too far, than have to deal with not getting the result you wanted.

OK. Thanks.
Why do you ask if it is below 100?
Using my CYA test, it looks to be greater than 90; but some of the markings on the sample tube have rubbed off, so it's my best guess.

I am draining the pool now and will use your 2/3rds guidance.

 

[Oly]

How certain are you of your actual CYA ppm?
It is a common error to drain your pool to lower your CYA assuming you know the actual ppm only to find out that your CYA is still too high after all the time, effort and $.

 

[Rancho Cost-a-Lotta]

Best to try a diluted sample to make sure you're CYA result is accurate. From the test directions:

If your CYA level is 90 or higher, repeat the test adjusting the procedure as follows:

1. Fill the mixing bottle to the lower mark with pool water.
2. Continue filling the mixing bottle to the upper mark with tap water.
3. Shake briefly to mix.
4. Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark.
5. Continue the test normally from step 2, but multiply the final result by two.

 

[JJ_Tex]

Why do you ask if it is below 100?
Using my CYA test, it looks to be greater than 90; but some of the markings on the sample tube have rubbed off, so it's my best guess.

100 is the maximum reading of the test kit. We have seen too many people drain and refill their pool and not get the desired results, because their CYA of "100" was actually 180.

Rancho beat me to it, but follow the steps above to find out your real CYA amount before you finalize your drain/refill plans.