I'm just using drinking water from my tap. It comes from the mains supply and is the only practical option I've got.
Plants seem to like it going from past experience.
It makes a great cup of tea too,
mmm tea ;-)
Thanks pinkus,
I've got a cheap liquid test kit.
13 litres of water (hard) and 1ml ph down seems to bring the water down to 6.4
Gonna try that level then.