Quote Originally Posted by chem geek View Post
The use of calcium to reduce foaming makes sense in spas (waterbear has recommended 120-150 ppm and that seems to work well in spas) where foaming can be more common due to the low water volumes so high bather load, but in a pool it's not normally a problem as Ben noted.
I'm guessing that this is actually creating what is called in household water, hard water, which is why water softeners are popular (we have one). Hard water is notorious for being difficult to form suds in, for breaking it down quickly, and, of course, for leaving scale on everything. So it makes sense that if you make the water harder, foaming/sudsing will be more difficult. I realize this is different in that hard water is usually other metals, particularly iron and copper, but calcium is, of course, a highly reactive metal, but a metal nonetheless.