We had this tip passed to us by our allotment officer and felt it was too good not to share – (thanks Fiona).
If you have a downpipe against your building it is quite possible, with a little ingenuity, to collect rainwater. Perfect for flushing toilets but please don’t drink it. You could even go a step further and get hold of or improvise a water butt. In heavy rain you can collect a lot of water this way in a short space of time.