I recently bought a house with a 12,000 gal pool and have been studying this site to learn how to take care of it. I just got a Taylor test kit to check the water. The issues I need to address are high CYA ( approx 200 ), high CH ( approx 700 ), and high metal content ( heavy stains on steps and light stains on walls that clear up with vitamin C ). My plans are to drain and refill between 50% and 75% of the water to bring down the CYA and CH, and treat the metal stains with ascorbic acid and sequestering agent.
I need advice on where to start. My initial thought was to deal with the metal stains first so all the metal will be sequestered in the water before draining. However, my tap water's PH is over 8.0 and I am concerned that the stains will come back as soon as I refill and require a second treatment.
What do you think? Drain first, ascorbic acid first, or something complete different? Thanks.