Oh, how I wish I had rain water. Any amount. Yearn, yearn...

:-). In Washington, DC we are in the frustrating part of the year
where it is very hot, fairly dry, and where the weather forecast calls
for "chance of thundershowers" almost every day (but you don't know
whether you'll get any).

Forgot to mention that the info about testing kits from nursery
requires that one use purified water. Sounds logical, not to get
confused by extraneous minerals, but just another nuisance on this
small-scale test, to acquire that kind of water.

That's another variable. I'm assuming rain water is good enough given
that's what the plants are going to mostly get (we don't irrigate our
garden heavily), but I'm far from an expert on these things.