by the way, here is a picture of the pool
http://s981.photobucket.com/albums/ae297/emh1960/

When the salt cell makes chlorine it also throws a base product out that causes the PH to rise constantly.
Yes you will be adding alot of acid. In high use time you should add it 2 to 3 times a week.

Just a pb, will all that muriatic acid damage the pool, or the swimmers?

No, pour it in front of return lines and pour slowly, adding small amounts. Never add to the skimmer.

That high ph over time will damage the finish and possibly the equipment. Adding acid is how you bring it down.

It is all about keeping your pool balanced. The better balanced the better it is on the finish, and the bathers.