I just changed the water in a 18/36 Vinyl IG pool with 18,000 gal capacity. It has a 1/2 hp pump; sand filter; and pentair 300 Chlorine 3" tab feeder. When I first tested after the refill FC: 0, PH 7.2 and A: 120,
I used the pool math to determine what I needed to add to the pool. I use granulated Trichloroethane in addition to the 3" tabs of trichloroethane in the feeder. For the past three days I have added 10 oz in volume granulated Trichloroethane dissolved in a bucket and added to the pool. After the first application the next day my test readings were FC: 0, PH :7.1, A : 140. The third day ( today) the readings were FC: 0; PH 6.9 and A: 160.
I am aware that the trichloroethane can lower the PH. I just don't know what to do to get the FC up to a 4 reading, maintain a PH of 7.2 - 7.8 and the A below 120. Would appreciate any guidance you can give me. I read that because I have a vinyl pool I should not be concerned about CYA. Does the trichloroethane have it in it anyway.