I need some help.....please

[chem geek]

We deal with high CYA levels here in AZ all the time. You're best to drain most of the water out and get it back under control that way but remember, the higher the pH, the less effective your Chlorine will be. At 8.0 only something like 24% of your chlorine has killing power and with CYA being more than double it's like you have 0 free Chlorine but at 7.4, you're double that. Don't be afraid to take your pH down to 7.2 temporarily to gain more killing power out of your free Chlorine as well.

This is an older post, but just to clarify for others, it is not true that the higher pH reduces chlorine's effectiveness as much as indicated when CYA is present. While the active chlorine (hypochlorous acid) concentration drops roughly in half from a pH of 7.5 to 8.0 when there is no CYA in the water, it only drops by 15% when CYA is present. This is because CYA is an active chlorine (hypochlorous acid) buffer. Graphs showing this effect are in this post.

 

[Patrick_B]

Thanks chemgeek, this is a very good reminder and excellent information.