Why is My Pool pH Test Purple? You Might Have Too Much Chlorine!
When testing for pH levels in a pool, you may get a reading beyond what’s indicated on the color comparator tube or strip. Instead of the reddish-yellow color that is supposed to show, the pH test is a dark purple.
This typically indicates a false high pH reading and has more to do with high sanitizer levels than anything else.
What Does it Mean if a pH Test is Purple?
You are likely seeing a purple pH reading because there is too much chlorine, or bromine, in the water!
Free chlorine (FC) levels of 10 ppm or higher and bromine levels of 20 ppm or higher can react with the phenol red indicators, which will cause a purple color to develop in the test.
This is one of the main reasons it’s recommended to balance pH before shocking your pool because pH tests are unreliable with large levels of sanitation in the water.
How to Retest pH Levels with High Chlorine
The best and most effective way to retest pH is to wait until your chlorine or bromine levels have dropped to recommended levels. They will drop naturally over time.
Another way to retest is by adding one drop of sodium thiosulfate, a chlorine neutralizer, to the test. For Taylor test kit users, this is R-0007, which is used in testing total alkalinity (TA).
However, remember that sodium thiosulfate has a high pH level. Adding more than one drop to the test can also create a false high reading.
Don’t Stress over a Purple pH Test!
High levels of chlorine aren’t anything to stress over. It’s no different than when you need to shock your pool.
Just let the levels drift down naturally, and keep testing the pool to ensure your levels are always balanced!