I am still trying to get my alkalinity down. I have an above ground pool (about 5500 gallons) 18X48. My alkalinity readings are still around 280. I have just been adding 1 cup and sometimes 1 1/2 cups of acid but my ph is only dropping down to 7.2 to 7.5. Can I add 2 cups at a time or that too much? I don't won't to ruin my liner.