Anyone know about recycling "grey water"? Or collecting rainwater to use?

[bohemianbint]

I mean, seems mad not to take advantage of all the free water that's coming down this month!

we got garden water butts from the council very cheap - you connect them to the downpipe from the roof gutters.
Grey water - you can do it DIY or have an underground tank / collection system fitted.

hmmm....we live in a terraced house with a tiny yard so don't think the underground thing is an option! Is it quite expensive to set it all up?