Chlorine, Bromine & pH Testing in Pool Water
Tablets & Liquids
The testing for disinfectant (chlorine or bromine) and pH in swimming pools and whirlpools must be performed once every two hours while the pool is in operation. The results must be kept in a bound log. The disinfectant and pH tests are also required when a microbial sample is taken (N.J.A.C. 8:26-7.7 & 7.12).
The Phenol Red compound is used for pH testing, and DPD reagents are used for chlorine and bromine.
Both DPD and phenol red can be obtained in tablet and liquid reagent form. Your field test kit is designed for use with one form or the other. Do not mix the different forms of testing.
Garden State Labs has tested both tablet and liquid reagents. We have found that when you are using fresh tablets or fresh liquid reagents you will get similarly accurate results. However, our experience has found that liquid reagents tend to age more rapidly than the sealed tablets.
This disparity has caused occasion where significantly different results were obtained. Typically aged liquid reagents yield a lower disinfectant level than the tablet. For example, and expired DPD liquid will give a 2.5 ppm chlorine while the DPD tablet 5.0 ppm.
Garden State Labs periodically checks the accuracy of the tablet reagents which we use for our sampling and analysis. We have found the tablets to be accurate. Do not remove the tablets from the foil until testing, this would cause the tablets to rapidly age.
We strongly recommend that tablets be used to get consistently accurate results