We have an 18,000 gallon pool, in ground with vinyl liner.
Hayward DE filter with a Hayward Super pump.
pH 8.0, chlorine 1.0, water crystal clear.
At the start of the season, we had no chlorine, but normal levels for other tests. When we began shocking the pool however, it became unable to hold any chlorine at all. We were told by a pool store that we needed to reach the chlorine demand and began putting tons of dichlor and trichlor tablets and granules into the pool. Well, not surprisingly, the pH of our pool went so low that the test strips no longer read it, and the stabilizer is at least 150 ppm.
After putting ten pounds of pool store pH up (sodium carbonate) into the pool, the pH was still too low to read, but the alkalinity had risen to 180 ppm. That is when we gave up on pool store chemicals and stumbled upon this website.
We added 17 boxes of Borax, which, thankfully, raised the pH to ~8.0 (admittedly a little high) but either latent effects of the pH up, or (less likely) the Borax, raised the alkalinity to even more obscene levels. We also switched to unstabilized chlorine in the form of bleach (at this point the pool would still not hold chlorine). We did one dose of 2 cups muriatic acid last night to start lowering alkalinity, and thankfully, the pH came back up after aeration as it should, although we're putting off lowering alkalinity for now.
As of today, we added 121 oz 8% bleach at 11:30, which maintained a chlorine of 1 ppm until 3:30, when we added 121 oz more. Hopefully this is a good sign, but bottom line, we just want the pool to hold chlorine the way it should and need to be able to maintain it for the summer.
I will never go to a pool store for guidance again.