That is what I was doing with my test kit. I took 4 ounces of pool water and added 12 ounces of tap water from the faucet (I know should have used distilled). Then I tested it to read around 4. Multiplied the 4 times 4 and translated that to read 16. Does this not work with that type kit? Even if I use distilled water? What about Kroger purified drinking water? I do not have the OTO test kit. I would be more likely to order the reagents you described above. Where can I get cal hypo?