The vinegar will act as a buffer for both the water, and the soil pH. It's best to get a reading on your runoff water first, then buffer the tap water so that it'll slowly bring the runoff to a desirable level. You shouldn't, however, try to raise or lower an extreme soil pH all at once. Doing so can send the roots into a state of shock. You'll want to adjust the pH over several repeated waterings. By the time you've brought it back to an acceptable level, you'll have a pretty good idea about how much is needed to keep everything in a good range, and how often a buffering solution should be applied. Most fertilizers cause pH to fluctuate as well, so keep that in mind when you use them.

Take care. :jointsmile: