mooseman July 20, 2012 08:37 PM Very nice! This is one of those "why didn't I think of that?" inventions. Gadgeteer July 20, 2012 08:39 PM A virtually cost-free alternative is to just capture the otherwise wasted water in a pitcher, bucket or cistern. Then use that later to water the garden or even flush the toilet. Slowburn July 21, 2012 04:36 AM The efficiency of the hot water loop system is dependent on how well insulated the loop is and how the water is circulated.The BYPASSER system looks to be expensive and/or failure prone. If you are worried about wasting the water run the sink and tub/shower drain into a cistern for flushing toilets. JSmith July 21, 2012 10:51 AM In about... 20 years or so (depending on the houses that want to catch up) we should have something like this, just 1 Tap that you can choose either Hot/Cold or a set Temperature (Warm).No more being cooked alive in your bath, trying to get the balance of Hot and Cold only to realise you've put too much of the other in.Good News christopher July 22, 2012 10:16 PM Better to waste it - nobody wants to drink the sludge that's been waiting stagnant in your pipes absorbing heavy metals all day/night ... go for the fresh stuff that flows in afterwards. William Blackburn July 22, 2012 11:07 PM Perhaps neat. But really if you do a life cycle analysis of all of the extra bits involved, I wonder if this comes out ahead? agulesin July 23, 2012 08:01 AM Good idea but I like the Chilipepper, a device available (?) in the States which pumps water back to the cold pipe (and therefore to the heater) until it reaches a set temperature, where an alarm is sounded. Turn on the hot tap and Voila!http://www.chilipepperapp.com/I'M against storing the water as you have to remember to use it - difficult to remember to scoop water from the store when watering plants etc. Darryl Petters July 23, 2012 01:30 PM There is a very simple alternative that does not waste water - see http://www.homedepot.com/h_d1/N-5yc1v/R-100426993/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=hot+water+by-pass&storeId=10051 Les LaZar July 23, 2012 08:12 PM Darryl, While a circulating hot water system does not waste water, it does use more energy: The electricity to run the pump and that to re-heat the circulating water (even if the pipes are insulated). Every solution has it's pros and cons. I haven't seen a "perfect" solution yet. Charles Bosse July 24, 2012 03:08 AM Why can't we just use Peltier devices to instantly heat our water at the tap? Four large ones and a good copper block with some fins into the water would easily pass enough heat to get the water at least up to a nice warm temp on demand. Anything else could have an internal heater (mostly they do). Outside the US even showers mostly have at-output heat anyway.