OK - strange to me. While fighting a mustard algae outbreak with high chlorine shock levels (low 30's) I encountered strange behavior with the drops test. Morning test. Rinsed the vial in pool water, added 10 ml pool water, tossed in the powder, and water flashes slight pink and then returns to clear without adding any drops.
so, I toss it out, rinse the vial, and repeat. This time, the solution turns dark pink and I proceed to record a FC level that is consistent with the bleach I added, etc (31 one morning and then 25 the next). This has happened two mornings in a row, but not for my evening tests. I rinse my vial in pool water before after each test.
Am I doing something wrong?
pH 7.2 - 7.3