We are constantly told that investing in a water butt to water our gardens is a good thing, it saves water and hence the planet. What is never mentioned is the fact that when you need it most, your water butt is probably not going to be much use to you. When it hasn't rained for several weeks and the inevitable hose-pipe ban is in place, you water-butt won't have a drop of water in it. Because of this, my water butt isn't getting filled up with rain water. Although the general consensus seems to be that using grey water for watering your garden may not be a good idea, as ever I decided to ignore any advice given to me and hooked our water butt up to the outlet from our bathroom. I'm not sure all houses are configured like ours, but the used water from our sink and bath goes out through a couple of pipes into a drainpipe so using this for the water butt was very simple.
And it seems to work fine. The water can smell a bit, but it doesn't seem to kill our plants and we can water the garden without feeling any guilt. One thing, remember not to wee in the shower... Although I'm sure you'd never do such a thing.