Advice for using rainwater

I use quite a lot of Rain Water now and my suggestions to you would be to let the rain fall for a good hour - after a period of no rain, to let the roof get a good 'wash' - before you start to collect any.

In my opinion Lead isn't the worst of the heavy metals we encounter - after all, we wrap our plants with it, don't we? I seem to remember reading that it's the oxides which come off the lead which are the potentially more harmful (so another good reason for letting the rain wash that off before you start collecting the water). I let mine run through a CCB (Block Carbon) filter in a housing 'stolen' from an R/O pre-filter set up, I really would like a solids pre-filter ahead of that as the Carbon is potentially blocking it up too quickly - more so than it would if the solids were taken away beforehand anyhow...But that's for the future and not totally essential anyway.

You might want to consider putting in some floating plants - especially Water Lettuce, these are renowned for removing much Heavy Metal deposits from water...Russell assures me they will even remove Arsenic! (I wonder who discovered that one!).

Assuming your water butt has a tap it will be situated a few inches off bottom level, this is good as it leaves the sediment which builds up on the bottom to remain undisturbed.

I'm wondering about your reading of 7.8 for the pH...really Rain Water should be, at best, neutral (7.0) - could it be that your test kit is a little 'out'?

Just some thoughts - no doubt someone will be along later to help you more comprehensively.

John