CYA level extremely high - need to drain / refill pool but have questions


Gold Supporter
I did a diluted test. I followed these steps-

1. I filled the collection tube (#9191) with 7 ml of tap water and 7 ml of pool water, mixed, then removed 7 ml of the diluted mixture.
2. I added 7 ml of R-0013 to the diluted mixture and mixed that solution for 30 seconds.
3. I went out and, with my back to the sun, slowly added the mixture to the small comparator tube until the black dot disappeared. This occurred at 100, the first line on the register.
4. I multiplied 100 x 2 to get my result - 200.
That means it could be ABOVE 200. Try a third dilution. Granted the error increases with the dilution, but it will give you a more valid number to calculate how much you need to drain off. Here is the procedure for doing multiple dilutions when the CYA is over 90:
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Jun 30, 2020
Frisco, TX
I'm pretty confident that the pH in my water is good now. I bought one of those meters that Marty recommended from Amazon. So far I love it because it sure beats trying to interpret the colors for the pH test. It came back with a result of 7.7. So I think I have my acidity issue resolved. It is a tad above the acceptable range now but much better than it was.

Regardless, I think I am going to rip the band aid off and drain/refill this weekend so I can start fresh and be able to rely on all my test results going forward. We'd like to do the no drain water exchange. We did buy a 1/4 hp sub pump - should we return this and rent a pump with a slightly higher hp (like 1/3 or 1/2) or would this 1/4 hp sub pump do the job for the no-drain exchange method?

The instructions for efficiently doing the no drain water exchange are also murky to me. For instance, do you have to get a separate test kit to find out the TDS and salt content of the fill water? Has anyone done this method that can advise on any pitfalls?

Lastly, if the delta t score is lower than 5, which I assume it's likely to be just based on water temperature alone, would it just be better to rent a high power pump, drain the pool in the late evening, and fill it overnight?

Thanks again for all your insights.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If your pool is not salt water (as it appears it is not), just assume the pool has 1000 ppm salinity.
CH you should have from your kit. And the CYA. Those items are the bulk of TDS

I have a 1/2 hp sump pump. The controlling factor is the diameter and length of the hose for your effluent from the pump. If you can get a 1" hose and keep it short, you will get pretty good flow rate, even from your 1/4 hp. But if you try to use a 5/8" hose that is 100' long, your flow rate will be tiny.

In your area, if you do not have shallow water table, a quick drain using a high powered rental pump and then refill would be the easiest. Is there risk? Sure, all pool drains entail risk. But if you start the drain later afternoon and turn it around filling as quickly as you can (multiple hoses, even a neighbor?), the risk is low.
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