Hi, I've read the forum and pool school for information for some time, but I have an issue that's confusing me so here's my first post/question. I'm in El Paso, TX and opening up early so I can take advantage of the solar cover to have the pool warm enough for use by March 25 or so.
After getting it cleared up my numbers were: Cl 4ppm; pH 7.5; TA 170; CH 450. The pool is 20k gallons with 1.5hp Hayward Super II and S244T Pro Series sand filter.
To treat this I drained 2 feet from the pool and after refilling my numbers were TA 160 and CH 330 so I added 50 oz. HCl to lower the ph to 7.0 and began aerating. My pool is equipped with 4 fountain spouts so aerating is fairly easy. After 36 hours the pH came up to 7.5 again and the TA is now 110 (hooray for me).
The reason for my question is that I have continued aerating during the daily cycle of 6.5 hours for 3 days now and the pH is still on 7.5. I had hoped to let it get up near 7.8 and add more acid to 7.5 just to see what it would do to the TA. I'm confused about the pH staying at 7.5. Is there a component that I'm overlooking that would cause the pool to act like it's buffered? I'm open to any suggestions.