A method I have for saving water from my greenhouse. I turned the rubber lid of the water barrel upside down to catch the water, in the centre of which I made a 4cms hole, into which I stuffed a plastic pan scrubber, to act as a filter. I then ran a length of hosepipe from one barrel to another, each end weighted down, to reach the bottom of each barrel, after flooding the air out of the tube. The water will then level off in both barrels. After "FIVE" years and keeping the the barrels covered, without further attention, the water is still clean and sparkling to use. More barrels could be added if required.