A new device could help cut the amount of water wasted whilst water from a hot tap is warming up. The invention, by a student at Brunel University in London, detects the temperature of water when a hot tap is turned on and sends the water into a pressure tank until the flow reaches the required temperature. Inventor Mitch Gebbie said the tank could store five litres of water at a time, the equivalent of two 30-second bursts of a tap. This would cut the average household water usage by up to nine litres per day. Its five per cent of your annual water bill that youre pouring down the drain, thats the average estimate, although obviously its going to vary between different households and different peoples uses, he said. The device uses a microphone to detect when the tap has been turned on and temperature is measured through thermally conductive copper pipes. A valve diverts the water into a tank connected to but at a higher pressure than the cold supply so that, when the cold tap is used, water from the tank empties back into the pipes.Gebbie said the system was designed to be easily fitted in existing properties. There are things that you put on the bottom of the boiler that restrict the flow rate until its hot and you use a third of the amount that you would usually waste, but this is 100 per cent, he said. Water-return systems that have a small pipe that goes back to the boiler have to be implemented when the house is built, whereas this is retrofittable. Gebbie is now hoping to develop the system to place on the market.