How to Test Swimming Pool pH With Phenol Red

Phenol red is a chemical used to test the pH balance in swimming pools and spas. It is available in a powder, a liquid and, most commonly, in tablets. To test the pH balance in a pool, use a pool tester or dip cell with phenol red tablets.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Pool tester or dip cell
• Phenol red tablets

1. Take the top off the pool tester. Fill the test cell chamber with water. Shake the tester vigorously and dump the water out of the tester.

2. Submerge the pool tester cells into the pool to sample the water.

3. Put one quick dissolving red phenol tablet in the chamber labeled "pH Test Cell." Replace the cap on the pool tester and shake it vigorously to dissolve the red phenol tablet.

4. Wait at least 15 seconds. Lift the pool tester toward the light to read its value. The ideal range for swimming pool water pH is between 7.2 and 7.8. Add the necessary chemicals to adjust the pool's pH.

5. Repeat the process until the pool water gets a normal pH reading.

Tips & Warnings

• Phenol red is occasionally labeled as "Guardex Solution #2."
• Keep phenol red out of children's reach. Phenol red may irritate the skin and is harmful if swallowed.