Ok, this is one I have been wondering about for a while, what is it about swimming pool chemistry that tends to require the addition of acid to maintain pH. And more importantly why is there such a wide variation in the amount needed. I ask because my pool needs very little acid to maintain pH (around 1 quart per year of muriatic acid, although since it is so low I do tend to use dry acid instead for convenience) vs some pools that seem to need that much acid each day. My standard method of chlorinating is use of 6% bleach, plus very occasional use of dichlor when I also need to boost CYA (something under 5-10 pounds per year if I don't have a water leak). Any thoughts on why there is such variation, and is there anyone out there that uses no acid at all?