Quote Originally Posted by chuck9997 View Post
I failed to check the PH before adding the bleach.. can I still get a true PH reading with CL level high? Right now the test says PH is over 8.. but the CL is high.
A high chlorine level can lead to a falsely high pH reading so you'll have to wait for the FC to get below 10 ppm before getting an accurate pH reading. The chlorine itself temporarily raises the pH, but the high FC level also bleaches out one of the two dyes in the pH test causing it to typically be misread too high. Taylor talks about that in their Pool & Spa Water Chemistry booklet:
FALSE READINGS: high levels of chlorine (usually >10 ppm) will quickly and completely convert phenol red into another pH indicator (chlorphenol red). This new indicator is a dark purple when the water's pH is above 6.6. Unfortunately, some pool operators mistake the purple color for dark red and think the pool water is very alkaline and wrongly add acid to the pool.

When a sanitizer level is not extreme, only some of the phenol red may convert to chlorphenol red. However, purple+orange (for example, pH 7.4) = red. This error is more subtle as no purple color is observed and the operator does not suspect that a false high pH reading has been produced. Some operators neutralize the sanitizer first by adding a drop of chlorine neutralizer (i.e. sodium thiosulfate). However, thiosulfate solutions have a high pH and, if heavily used, may cause a false higher sample pH.
The Taylor pH test has some special chlorine neutralizers in it such that they don't affect the pH very much, but even these don't work at very high FC levels so generally you can't trust the pH test above around 10 ppm FC.

Richard