First off let me tell you this site is fantastic! This is one of the few forums where people get good consistent answers.
I bought my house with this pool about 3 years ago and at the time the pool was about 4 years old. The previous owner hired some lame company to do his chemicals and they had no idea what they were doing. During the second month I owned the pool the chemical people came out and said that they would not service the pool anymore until I drained some of the water because they were dumping so much chlorine in the that something must be wrong. They couldn't explain to me what was causing the problem. I didn't have them come back again. I then took on the challenge of keeping up the pool myself with a cheap test kit. Everything seemed to be okay until this year. After not paying enough attention to the pool during the winter (if you call it a winter since I live in Tucson), I have been battling a black alge problem. After reading this forum, and realizing that my pool was eating chlorine like a fat american at a chinese buffet I decided to drain 3/4 of my approximate 14,000 gallon pool. I received my TF-100 kit today and have some interesting results.
TC=1 (.5 with the quick test)
I tested the CH of my tap water and it was only at 100. I added 15 floz of muriatic acid to lower the ph and 3 oz of 60% chem-tek shock quick. I'll check the readings again tomorrow and post.
My major concern is that the CYA is pretty high for having drained 3/4 of the pool and I am concerned that in no time it will start eating chorine again.
Could the high CH reading be due to the plaster in my pool breaking down? It is at the end of its life expectancy and with the previous owners ineptitude it may be beyond repair. I am currently getting quotes to refinish the pool with pebble-tec to help with the maintaince hassles.
What is the best way to combat the black algae problem with these results?