Quote Originally Posted by PoolDoc View Post
If you used the 'cloudy water' test for CYA (melamine precipitation), and got a zero result . . . it's zero. The remaining question is, did the CYA go to nitrogen gas (no problem) or ammonia? If it's ammonia, you'll see high combined chlorine levels, and low free chlorine. You have to use a DPD test kit to get good info on that.
I have the same problem: my CYA went to zero (using your test kit and the melamine precipitation test) and I have a high combined chlorine level. This was tested after running the pump for about 24 hours, so there are no issues with uncirculated pool water. My question: what do I do now? I added a bunch of chlorine and the free chlorine level is about 1 while combined is 3 (the daily test kit shows 1 even though I thought that this measured total chlorine).

All other levels are good (alkalinity, pH, calcium).