My pool is abotu 25k gallons and I needed to lower my PH in order to airate my water to bring my TA down. My PH was 7.8 and my TA was 160. I dumped a gallon of Muriatic acid in the pool last night by carefully pouring it so the return would spread it into the pool. This dropped my PH to 7.2 when I just measured it this morning. Of course after pouring in the entire gallon last night I read somethign where ben suggests NOT dropping it all at once...so in the future i will be adding it in 1qt doeses. Figuring each qt will provide about .15 drop in PH.