Low TA, high CH, low PH. black spots

[danny_b]

Hey guys my pool has been good, but due to living in phoenix I have high chlorine use, high evaporation, and high ph, TA, and ch in fill water. I know its getting time to drain and refill as the CH is really high. It has been 2 years since last drain and refill. My ph and TA always drifts up, so I add 64 oz of MA 31.45% weekly to try to drive TA (usually 5-6) down to slow ph rise. This weekend I added MA, started vacuuming and brushing pool, and noticed black spots that won't move. So I grabed a trichlor tab and rubbed the spots and didnt do anything. Normally I test every week before I add ma. Today I didn't. My test results after are.

FC- 5
CYA - 50
Ch- 1200
Ph - yellow ( off scale low)
TA - 1
Salt - 5000

I do not have a SWG, I use stenner. High salt is left from liquid chlorine use.

 

[danny_b]

I know that I OD muriatic acid, which is possibly due to a bit cooler weather, which in turn need less top off water, which in turn lessened my need for ma as TA didn't climb as usual. I'm assuming the black spots are copper ? I have no copper pipe except a small stub up for top off valve. I do have 4 bronze valves, one for aereator and 3 for wall sconces. I put some pure vitamin c powder on stain and didnt do anything.