A test kit is used to check the free chlorine and pH of the pool water. Some test kits also measure total chlorine, total alkalinity, calcium hardness and cyanuric acid. The DPD test kit is available in a manual version, in which the test water is compared with a colour scale, and a photometric version, in which the value is displayed digitally to two decimal places.
Every test kit is supplied with test tablets as follows:
DPD no. 1 measures free chlorine
DPD no. 3 measures total chlorine
Phenol red measures pH
Where the chlorine level is above 5 ppm (mg/l) the test water is bleached. The result may then indicate that there is no chlorine in the pool. If you suspect this, you can dilute the test water with ordinary tap water.
Avoid touching the test tablets with your fingers as this may cause incorrect results.
Test strips are dipped in the pool and their colour of the measurement areas is compared with the colour scale on the pack. For correct readings, move the test strip back and forth in the water for five seconds. Take the strip out of the water and wait five seconds before comparing the colours.