Smartphone Pool Calculator
Whatever your swimming pool is filled with, you're soaking in it. So make sure it's not lemon juice or an alkaline mini-lake. Whip out your iPhone, load this Pool Calculator
(US$5) app, and find out what you need to do to get your pool's pH, chlorine level, and other chemical properties into optimum balance. The app provides recommended levels, ranges, and computations for a multitude of basic chemicals.