Many people ask about pH regulating their tap water and I thought to share some links and information regarding the choice of acids and bases that are available. The first thing someone should do is to examine their municipality's Water Quality Report generally found online. Take some time to look it over and familiarize yourself with what you are actually drinking and bathing in. A lot of the time communities use hard water. Hardness is the degree of calcium (and magnesium) carbonates and bicarbonates in the water. These carbonates are forms of CO2 that are stored in the water when coupled to calcium, but take a moment to think about what calcium carbonate is. It makes up eggshells, exoskeletons, seashells, plaster, concretes, and is derived from limestone. Once you add an acid to the carbonates, you release CO2 (initially as carbonic acid) and form a calcium conjugate salt, which becomes available to the plant. This table shows four common acids used by growers. Note * that citric acid is the only acid used to maintain organic certification and that it is also a carbon source which microbes can use as energy. The table is linked to reference. I also noticed the cool calculators hosted by UNH (linked): Very helpful tools ! By plugging in your water's alkalinity (found in the water quality report), the alkcalc will determine the amount of acid you need to add to bring the pH to what you want it to be. It will also indicate how much nutrient value you have added by doing this. I am aware other apps also exist (Hydrobuddy, for example), but the calculators I linked are really easy to use and you don't need to download anything.
If you're on a private well and do not have a recent water test report. At a minimum you want to measure your pH and your total alkalinity. The reason this Greenhouse production calculator doesn't give a lot of information on citric acid is because it is not cost effective on a large scale. These are the test strips I use to test total alkalinity. waktoo put me on to these.