Instant hot water??

A friend of mine is tired of waiting for hot water and wants to install a instant hot water system in his house, for a few hundred bucks.
At first I thought this is impossible without installing a separate pipe, circulating the hot water to the heater in a loop. But, Google tells me that these new systems use a recirculating pump and a thermostatic bypass valve at the farthermost hot water outlet.
When the water at the hotwater faucet cools to 85 degrees, the pump activates and the valve pushes the previously hot (but now cooler) water into the cold water pipe.
This system claims enormous savings of water that would otherwise go down the drain (until the hot water arrives at the faucet). It seems to me that the system saves water at the expense of constantly heating all the water in the hot water pipes: A great waste of energy.
An instant hot water system makes sense in an apartment building or hotel, but not in a home.
Furthermore, this system would constantly push 85 degree water into the cold water line. Yuk!
Has anyone tried this system?
http://www.homedepot.com/prel80/HDUS/EN_US/diy_main/pg_diy.jsp?prod_id165 8&cm_ven=hd_goog&cm_cat=Search&cm_ite&-6-11-instant_hot_water-PR-20-161658
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Walter
The Happy Iconoclast www.rationality.net
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I have *Instant Hot Water. Its for Coffe or Tea. I could not live without it.
I think you mean those small tankless heaters. I used them in Hospitals, they work fine.

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No, I mean the retrofit systems that are all the rage. They do not use a return pipe. Try this URL:
http://rewci.com/whhohotwaci.html?engine ­words!992&keyword=%28instant+hot+ water%29
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Walter
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First time I've seen one.. Like all new things I wait and see what others have say on it.
There are far too many people out to re invent the wheel.

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Walter R. wrote:

that energy just to save a few seconds of waiting time and a small amount of water in a typical home situation.
I came up with all the same reasons as you, and I figured that if I had one I'd probably waste almost as much cold water as I'd saved on the hot water every time I wanted to draw a glass of cool water.
There's some yahoo who's been spamming the DIY newsgroups lately pointing folks to his website where he has a video showing how quickly and easily a young girl can install his undersink unit. Yeah, and how many of us have a handy 120 volt receptical under our bathroom sinks to plug his unit into? It'd take a bit of professional work to install a legal outlet there, wouldn't it?
I can understand the benefits of a proper gravity (or even pumped) recirculating loop with a dedicated return line AND good insulation on the pipes. That'd provide a sensible luxury for those willing to pay the original price.
Just my .02,
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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I am a plumber in houston & have installed several of these pumps. I think they work well. With the built in time i can set it to the clients schedule, so it wont be running 24-7.
Mike Dayter
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I think you have this system confused with something else, Instant H/W systems use gas fired water heaters that heat the water instantaneously, ie when an outlet is turned on the heater fires up and the only water heated is the water used, they should be fitted as close as possible to the outlets served. Putting hot water back into the cold water side does not sound correct, where does the water go? give me more details on this, where did you find it on google?

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