The testing for disinfectant (chlorine or bromine) and pH in swimming pools and whirlpools must be performed every two hours during operating hours and the results 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 color comparators used for pool water tests are DPD for chlorine and bromine and phenol red for pH.
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 them.
Over the decades, Garden State Labs has tested both tablet and liquid reagents. We have found that when you are using fresh tablet or fresh liquid reagents you will get similar accurate results. However, our experience has found that liquid reagents tend to age more rapidly than the sealed tablets.
This disparity has caused occasion for discussion with our clients having scenarios where significantly different results were obtained. Typically aged liquid reagents yield a lower disinfectant level than the tablet. For example the DPD liquid gives 2.5 ppm chlorine and 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.
Pool and Lake Testing Page
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