Drop test kit

A drop kit takes more time than strips, but you can trust the numbers more. You add reagent drops to a water sample and count until the color changes.

It is the best home tool for telling free chlorine from combined chlorine, and it reads high chlorine levels that strips cannot. Replace the reagents every year, since they go bad. Store the kit out of the sun and rinse the vials after every test. Keep a log so you see trends.