How long to wait to retest after adding chemicals?

I would like to know how long I should wait after adding chemicals (chlorine, CYA, Muratic Acid, etc.) before testing again for those items.

I have a 20,000 gallon gunite pool. If I add CYA Stabalizer to increase from 40ppm to 60ppm how long after adding it will the test results acturately reflect the new levels? I've heard to wait anywhere from 24 hours to 3 days (with pump running continuously).

What about when I add Muratic Acid to lower the PH. How long before I should retest to verify the change?

Thanks,
mike

For CYA, I'd wait at least three days. Chlorine and acid, I wait a few hours. May not be best accuracy, but it's close enough.

For CYA, I'd wait a week. Or at the very least about 5 days. CYA dissolves very slowly in your filter. If you retest for it too soon, it may have not all dissolved and you think you need more. Then, you end up with too high of a reading and the only way to lower it is to do a partial drain. Better to be patient with it.

Watermom

With chlorine and acid, I wait 2-3 hours. However, like Watermom says, CYA can take up to a week or so. Also, you need to make sure that you don't backwash the filter in that time, otherwise all the CYA will just be washed out and you'll have to start over.

Janet

Here's another vote for CYA = 7 days, other chems 3 hrs.

Michael

Thanks for all the replies.
Michael - perhaps you could/should add this info to the help section in your BleachCalc program.

I'll do that...right after I write the help section! :D

Michael