Quote Originally Posted by smallpooldad
Ok,

If we lower the Alk to 80 should we use a CYA adjustment for 50 at 7.5?

In other words should the indicated Alk on the test be higher?

Aloha
Good catch. I misread your earlier post where your real TA dropped from 120 to 100. Generally when we report TA on this forum we report the test measurement's Total Alkalinity that is not adjusted for CYA. If you adjust the TA for CYA, then this isn't TA anymore it's Carbonate Alkalinity instead (CA? -- could get confused with CYA or CH so we just don't use this). When we get all the numbers including TA and CYA, we can do the appropriate compensations as needed.

So yes, drop your actual measured TA from 120 to 100 and let the pH rise a little to 7.4 or 7.5 as a starting point. Then see how much acid you are adding to keep the pH stable. If it's less and if it seems like your fighting the rise in pH less, then this is a better alkalinity to be at. If there is little or no change, then you are experiencing something that we've seen on the rising ph levels thread and we don't yet have an explanation for it. So if the lowering of alkalinity doesn't help your pH rise and acid usage, don't sweat it. There isn't anything you are doing wrong.

Richard