The town water I use sometimes changes, it was at 5 deg. now its at 6 deg., I've seen it as high as 9 deg. I was told that it shouldn't go that high again because they had to shut down the oldest well (DER). The only test kit I use is API . I have a drop checker from the Red sea CO2 Pro kit and they say to use my tap water with the solution. As I read the posts here I'm now confused, if I use distilled water and CaCO3 to get a 4 deg. KH wouldn't the reading be incorrect from the drop checker?