False high pH readings when shocking--Some truths

[waterbear]

High sanitizer level cause false high pH readings. High chlorine converts the phenol red indicator used in just about all test kits and strips into chlorophenol red which has the exact same color changes as phenol red but at a much lower pH range so the dark red to purplish color occurs at 6.8 and the colors that indicate a 'normal' pH are below 6.8 down to the lowest which would be 5.4. 

With bromine,  adding chlorine converts the chlorine into bromine sanitizer which converts phenol red into bromphenol red and the same things occurs over a pH range of 5.2 to 6.8.

[THE DUDE]

At what FC reading would one disregard the PHreading or leave the ph  alone until the FC reading dropped off? In my mind, I thought I read above 10ppm FC.

[THE DUDE]

I hit the books and found my answer.

"The pH does not spike, it only seems like it does because of the chemical interference. NEVER try to measure pH when your sanitizer is above 10 ppm for a Taylor kit and some strips. Some other  brands are good up to around 5 ppm. Adding thiosulfate or another chlorine/bromine remover can help extend the range but will also not give a precise pH measurement since the addition will also affect the pH of the sample. "

[waterbear]

yes, I wrote the info you posted above.