pH reading and high chlorine

Demegrad9

Well-known member
May 27, 2017
362
Coventry, CT
Hi everyone, so I have the issue that I have to reduce CYA from currently 100ppm over the course of the swim season. I went about the SLAM process and got low ~0.5ppm overnight FCL. So I've been letting FC level come down and it's currently 17ppmFC. While discussing my more detailed situation in another thread I was warned that pH measurement will be off at high FC levels, so I started doing some search on that. I came across this old thread:

https://www.troublefreepool.com/threads/27716-How-to-test-pH-with-a-high-chlorine-level

So I tried some of the ideas using DI and Distilled Water and here are the results, maybe you guys can decipher this:

Straight Pool Water: 7.4
DI Water: <7.0 (Using R-0004 but test strips said 6.2)
Poland Brand Distilled Water: 7.0 (Using R-0004 and test strips)
Pool Water + DI water 1:1 Dilution: 7.0
Pool Water + Distilled water 1:1 Dilution: 7.2
Pool Water + 1 drop R-0007: 7.4
Pool Water + 2 drops R-0007: 7.5
Pool Water + 3 drops R-0007: 7.6

Basically all measurements were made with the K-2005 R-0004 pH indicator except where I used some test strips were noted to confirm. Other measurements:
FC: 17ppm (FAS-DPD)
CC: <0.5ppm (FAS-DPD)
TA: 110ppm
CH: 250ppm
CYA: 100ppm

So any thoughts? Or guesses as to what my ACTUAL pH is?