High CYA, drain 1/3 refill?

[Watermom]

Before you do a partial drain and refill, you might want to figure out just how high your CYA actually is. The limitations of the test will not differentiate readings higher than 100 so a result of 100 might mean 100, or 300 or 500 or ?? If it's super high, then draining a third of the water might not make that much difference.

Dilute the water sample one part pool water and one part distilled water and then run the test again and multiply the result by 2. If you still get a reading of 100, do one part pool water and two parts distilled water and multiply the result by 3, etc.

[fatstogie]

Thanks forgot that trick. I will dilute 50% with distilled water measure and repost.

[fatstogie]

I diluted 2/3rd's remeasured and it reads aproximately 38, so the pool must be around 114. Looks like I need to drain at almost 1/2?

[PoolDoc]

If your target CYA is 60, yes. If it were me, I'd just switch to bleach or cal hypo. But, I don't know what's available to you inexpensively, and I don't know what your calcium levels or equipment set up is. It's hard to use cal hypo long term, if you don't have a sand filter.