I would open up that main drain so that the high FC water can kill gunk in those lines. Just my opinion.
About the CYA, have you been adding water? I don't think so, but just checking that first. There is a +/- 10% error on the CYA test.
About the CYA, have you been adding water? I don't think so, but just checking that first. There is a +/- 10% error on the CYA test.