First, I have a TF100 on order, but am unlikely to get it this week. In the mean time, I'm using an HTH 6-way drop kit. Currently my CL test is at the upper limit of the test (5) I also have a box of HTH test strips, and a box of AquaCheck strips. All pretty much agree that the CL is around 5. (It's been cloudy the past few days and my CYA is around 70 so the CL is not burning off as fast as normal. Since I'm at the upper end of the test kit, I'd like to know if I'm actually above 5.
I'm curious if I can use half as much phenol red and effectively double the range of the test (making the top end 10 instead of 5) Since the kit requires 5 drops of phenol, I'd have to double the water instead of halving the drops, but the same principal applies.