This is the 4th summer with our pool, switched to the BBB method in year 2 and never looked back, never had a problem...until now. When I closed the pool in October I drained the water below the returns (approx. 18") in order to blow out the lines added 10 gallons of 8.25% bleach and a bottle of algecide- same routine I had followed the previous year with excellent results at the spring opening. We have loop-loc mesh cover so each spring we end up with diluted CH/CYA levels- good right? I use Cal-Hypo to shock early in the process until I hit the 250 CH range, then switch to bleach. I also use dichlor during the startup to get the CYA up in the 45-50 range.
Cover came off the week before Memorial Day, murky water but not terribly troubling based on past years. Started with dichlor to get the CYA up, lots of brushing and vacuuming, then to Cal-Hypo, finally to liquid bleach. After a week or so the water was clear and all of my numbers looked great, however there was yellow/brown "stuff" all over the bottom and walls of the pool. Brushing and vacuuming have faded the color significantly over the last month but still the pool surface looks terrible. In week two I decide that I must have mustard algae as we don't use algecide with copper or have a heater with tubes that could leak. Consequently I started on a mustard algae shock regimen that I have been keeping up for the past two weeks with no improvement (I was being the good, patient pool owner that always wins the day!). With a 30K gallon pool and mustard shock FC level of 27 you can imagine the $ I've spent on chlorine . Finally this morning tested for stains- vitamin C didn't provide any lightning of the stains nor did a trichlor puck. Finally put a piece of PVC on top of a brown area, added a couple of ounces of muriatic acid and waited. As you might guess, when I moved the PVC pipe the area under it was perfectly white... So I'm leaning towards the abscorbic acid treatment based on what I've read here. Sound reasonable?
I'm afraid I've damaged the plaster as the surface is now noticeably rougher. If anyone can offer an opinion as to how badly I may have hurt the surface (which was re-plastered 4 years ago) I would greatly appreciate it.
Current readings from the K2006- FC 6.5, CYA 30, CH 260, TA 90, PH- 7.0 (was 7.4 and I added a quart of MA to bring it down)
Sorry for the long post, thanks in advance for any observations/suggestions.