While boiling water does not remove nitrates, it does destroy KH. This means is has no resistance to acids or bases added to the water and thus holding pH stable is difficult to impossible.

How can I make my water safe? Boiling the water is the best way to ensure that it is free of illness-causing organisms. Bring water to a rolling boil for a minimum of one minute. When it cools, refrigerate the water in clean containers. (A pinch of salt per quart may improve the rather flat taste of boiled water). If you do not want to boil your water, you can disinfect it by adding 1/8 teaspoon of bleach (common household bleach containing 5.25 percent sodium hypochlorite) per gallon of water. Do not use bleach containing perfume, dyes, or other additives.
From http://www.mass.gov/dep/water/drinki...lfaq.htm#three