The test kit is perhaps the most valuable aid to the pool owner and enables him to keep his pool in proper swimming condition. An adequate test kit is one which includes both a chlorine and pH test.
Most test kits use the ortho tolidine test for total available chlorine. This test produces a yellow color varying in strength with the amount of chlorine present in the water. When the color produced corresponds to a chlorine reading between 0.3 and 0.6 ppm, the bather is assured that the pool is safe for swimming. Since chlorine dissipates rapidly in hot weather and under heavy bathing loads it is wise to test frequently to assure a sufficient chlorine residual. Just how frequently is best left to the individual pool owners experience. A colorless reading means that all of the chlorine has dissipated and it will be necessary to add more. A reading greater than 0.6 ppm indicates the presence of an excessive amount of chlorine and bathers should not be permitted to enter the water until the chlorine had dissipated to a safe level.
Tests for chlorine should be made about thirty minutes after it has been added to allow the material to dissolve and mix throughout the water.
The phenol red method is the most common way of testing for pH. In this test, the color changes from amber at low pH to purple at high pH, each color between corresponds to a different pH number. When the color produced corresponds to pH readings between 7.2 and 7.8 the water will be in proper chemical balance. PH tests should be made at least once daily and more frequently during periods of adjustment. When adjusting the pH be sure to allow enough time for the chemicals to dissolve and to mix thoroughly throughout the water before testing.