I've been monitoring some very low levels of FC all season (0-0.5). The manual for my SWCG says it maintains a 0.5-1.5 ppm range for CL. I've try to adjust the SWCG up when it reaches 0 CL to 80%-90% production. While the SWCG does seem to generate CL (tested at 5 right out SWCG), it's either being blocked or being eaten up; never getting above 0.5 CL in the pool. As an fyi, the pool is crystal clear.
The SWCG manufacturer says I may have phosphates so I tested and have about 1,500 ppb. I treated for phosphates (one treatment) but still have the CL issue. I'm trying to decide if I need to hit the phosphates or do I have a hidden algae problem (again, my pool is crystal clear).
Last night after dark I tried a test to see if the CL was being eaten up by sunlight or something else. I dumped in about 5 Gallons of 6% bleach after dark (should have brought my CL up to around 4). First thing this morning I tested and the pool's down to only about 1-1.5 TC (did not have time to do the CC test). Here are my numbers:
TC: 1.5 (morning test after 5 gallons of bleach the night before)
Do I need to shock so the CL holds over night or am I chasing something that does not exist?