On copper pipes, real damage from acidic water typically starts within 6 to 18 months, depending on how low your pH is and how much water you use. Here is what moves that date for your house, the order the signs show up in, why the hot water side goes first, why it is never too late to stop it, and why switching to plastic PEX pipe does not end the corrosion.
Test first, then buy only what the test calls for. Most wells need one or two systems. Sand takes a sediment filter; rust or black stains and a rotten egg smell take an iron filter; hard water takes a softener; blue-green stains take an acid neutralizer; bacteria takes a UV light. Of 344 well tests my customers sent in, more than half showed one of those problems or none. Here is the match, with today's price for each system.
You can test your water's pH at home with a strip kit (about $25) or a digital pH meter, and a certified lab test is the most accurate. The hardware-store strip kits only read down to about 5, so below that you need a meter or a lab. Here is how I rank the three tests, how to take the sample, and what your number means: below 7 is acidic, at 6.0 and up plain calcite works in any size tank, and below 5.5 it takes calcite with FloMag mixed in.
The best acid neutralizer for most wells is a Clack 2.5 cubic foot non-backwashing tank filled with calcite: it brings acidic water up to a pH between 7 and 8 with no drain line, no electricity and no moving parts. Here is my pick for each situation with today's price, when iron above 0.5 ppm calls for a backwashing tank, how your pH picks the size, when to add FloMag, and what arrives in the box.
A "pH water filter" is an acid neutralizer: a whole-house tank of calcite, which is crushed limestone, plumbed in where the water enters the house, that raises low pH well water to about 7. Google shows four things under that name, a pitcher, an under-sink cartridge, the whole-house tank and a chemical pump, and only the tank treats every pipe in the house. I go through which one you are looking at, why the limestone is the natural fix, how to find out whether your pH needs one, where the tank goes, and what changes after it is in.
Acidic well water is fixed by installing a whole-home acid neutralizer where the water enters the house, right after the pressure tank. Calcite alone works for pH 5.5 and above; below that, a calcite + Corosex (FloMag) blend. Here is how I know the water is acidic, what it does to the copper in the house, which size and mix your pH calls for, what to do if you also have iron, and why the water comes out a few grains harder once it is in.