Quote Originally Posted by Midnight View Post
1. Should I take a sample of water to the pool store to test for CYA and chlorine?
No. They can't help you.

First they cannot test chlorine at the levels you need; you can only do that with an FAS-DPD test. You can *estimate* levels with OTO, but that's all.

Second, your CYA isn't going to change that much. If it was 140, and you drained & replaced 1/4 of the water, it's now right at 100 ppm.

2. Can the pool be swimmable with a high cya for the rest of the season? (Maybe about 4 weeks left.)
Yes. As I've noted, I've been operating a LARGE (200,000+ gallons) commercial pool with CYA ~100 ppm and chlorine between 10 and 30 ppm, with ZERO problems or complaints. (These levels are 2 point code violations, but the inspector hasn't noticed because he uses test strips! He has noticed the pool looks really good . . . but that's been the case for years.)

However, you MUST run high chlorine levels. Since you have only OTO, you need to dose to orange, and let it fall to DARK yellow, and then re-dose to orange again.

The "Best Guess" page, linked in my signature block, explains all this.

3. What level should the chlorine be at to be safe to swim?
Safe? With CYA = 100 ppm, anything below 100 ppm FC is safe for people. Safe for swimsuits is probably below 40 ppm.