It may not be sexy, but this simple little toilet accessory may save a lot of water.  The standard toilet tank flapper can form a leaky seal, or simply lower too slowly to stop water flowing into your toilet bowl.  One estimate has leaky flappers wasting an estimated 11 million gallons of water a minute in the USA.

The weighted Greenflush valve closes much faster than the traditional flapper. The Greenflush, which is said to install in 30 seconds, is estimated to reduce a typical 2 or 3 gallon flush to 1 gallon.  It also works with newer low-flow toilets.

It sells for $19.95 – but hey if it works it will pay for itself very quickly.