Quote Originally Posted by Gerald C Koch View Post
Even if you live in an area with very hard water you can soften it by vigorously boiling tapwater for 5 minutes and allowing it to stand overnight. The temporary hardness (calcium ions) will precipitate out. The permanent hardness (magnessium ios) have no effect on photographic uses. The next day decant or filter off of the clear portion for use in developers.

Incorrect. Boiling the water increases the hardness up until you reach the saturation point, and then salts will begin to precipitate out. You will be left with severely hard water.

Magnesium and calcium ions act have almost the same reactivity.