Where we live, our water is high ph (8+) So I added enough vinegar to bring the ph down to neutral or slightly less (6.5 - 7). This does require a water test kit, but not a chemistry degree. For here (Moorhead MN), I added 1 Tablespoon per gallon of water.
Also, in regards to vinegar being a weed killer, I totally agree - in high amounts - not unlike fertilizer - too much fertilizer kills as well.
