Device could help save water while hot tap is warming up
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A new device could help cut the amount of water wasted while waiting for a hot tap to warm up.
The prototype technology developed by a student at Brunel University in London detects the temperature of water when a hot tap is turned on and diverts the stream into a pressure tank until the flow reaches a specified 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, and cut the average household water usage by up to nine litres per day.
‘It’s five per cent of your annual water bill that you’re pouring down the drain, that’s the average estimate, although obviously it’s going to vary between different households and different people’s uses,’ he told The Engineer.
The device makes use of a simple microphone to detect when the tap has been turned on, instead of a more costly flowmeter, and temperature is measured through the thermally conductive copper pipes.
An electronically controlled 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 turned on, the tank automatically empties back into the pipes.
Gebbie said the system was designed to be easily retrofitted in existing houses. ‘There are things that you put on the bottom of the boiler that restrict the flow rate until it’s hot and you use a third of the amount that you would usually waste, but this is 100 per cent.
‘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.’
He is now looking to develop the system into a commercial product.
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Readers' comments (25)
Crig | 28 Jun 2012 2:10 pm
I'm with Dave - I simply have a large plastic bottle under the kitchen sink and fill this up when I start to turn the hot water tap on. I can then use that water to water the plants, rinse veg etc - but not drink it. In the bathroom, we have a small bucket for the shower and that goes in the toilet so saves on flushing. Easy to save water and free to implement.
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Steve Gardner | 28 Jun 2012 2:16 pm
Mitch & Stephen,
Firstly I congratulate you for identifying a problem, offering a solution, and protoyping it - well done. With a couple of small mods, it could be a goer.
Secondly,
Dinos Kynigos H.T.I., MBA, MNI, CMILT, for all the letters, is offering bad advice. You cannot patent this as it is already in the Public Domain - doh!. Never mind, I've been in design and prototype manufacture for 40 years, so know how dispiriting it can be when negative comments are made, even though the prototype works. Smacks of N.I.H.
Best of luck for the future chaps, keep thinking and doing!
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Rob Powell | 29 Jun 2012 0:16 am
Do what we do here in Melbourne, Australia, after years of drought and stick a bucket under the tap, catching those few litres of cold water until it warms up. Then tip the water onto the garden, or into the toilet cistern, washing machine etc. It's not rocket science and a plastic bucket is a whole lot cheaper and doesn't need to be installed by a plumber.
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Dennis Jewitt | 2 Jul 2012 2:54 pm
Interesting discussion. How about the operating costs ? Is the power source a walwart or a 9V battery. Presumably the microphone has to listen all the time in standby mode and then each time the tap is used a couple of pulses have to be sent to the valve.
The device also doesnt save any energy and maybe there is a market for internal plastic liners to thread into existing 15mm pipework to reduce heat loss and volume.
I suspect the greenest solution is the plastic tub to collect and reuse the water that many already practice.
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Bjørn Verheijden | 5 Jul 2012 7:59 am
I like the idea as a start point, but a lot more thinking should be done before trying to put something like this on the market.
Using the excess water for the grey water circuit seems possible, maybe even using it for your washing machine.
(both toilet and washing machine have no end pressure in the system, so using the pressure tank as described would not be a problem)
As the water is already luke warm, the energy cost for running this one will be reduced (heat insulation on the tank is required). Shoving it into the toilet means that you'll dump the heating power that went into it straight in the sewers.
How feasable the whole idea is, depends on the cost price I think. A retrofit sounds nice, but is mostly far more costly then a integrated system new build.
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