Let's do a chlorine demand test. You'll need a cheap OTO kit, as well as the K2006.

1. Get a clean 5 gallon bucket or waste can. (really clean)
2. Put 4 gallons of pool water in.
3. Add TABLESPOON of PLAIN 6% household bleach; mix.
4. Test chlorine levels with OTO immediately after mixing. You should see a BROWN or DARK ORANGE color. If the color is orange, yellow or clear, you have a chlorine demand problem.
5. Test again after 1 hour. If the color is NOT the same . . . you have a chlorine demand problem

Don't use the K2006, at least the first time -- you'll use up too much reagent.