Measuring CH accurately using Taylor Kit K-2006 FAS-DPD


Gold Supporter
Jun 8, 2012
North East New Jersey
Pool Size
Liquid Chlorine
Question regarding Calcium Hardness. When I test for CH, the Taylor Kit K-2006 instructs me to stop counting drops (reagent R-0012) when the water turns from red to blue. But... my water turns lavendar/purple first, then if you add more drops it'll finally turn blue, but it takes a substantial more amount of drops to go from lavendar to blue. This color situation makes me doubt (a little) whether I'm tracking CH accurately. Does Taylor consider lavendar same as blue? Are they color blind? When do I stop adding R-0012 drops exactly? I ask this because my pool plaster surface (diamond brite, 15 years old) is rough and sharp to the touch, they're are calcium crystals that have formed all over the underwater surface of the pool and it can literally rip your skin off. I know that the sharpness in the plaster is a result of a CH problem (aggressive water), and I'd hate to think I've been recording the CH numbers wrong after all these years. Thx in advance.