EcoDrain heat exchanger makes good use of warm waste water
By Darren Murph 
posted March 26th 2009 5:59AM
posted March 26th 2009 5:59AM
[Via Inhabitat]
posted March 26th 2009 5:59AM
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It's called cross-current exchange. Your body does the same thing in the capillaries to maximize the amount of O2 going into tissue and C02 coming out of tissue. Score one for nature.
Not a new idea
http://gfxtechnology.com/contents.html
http://www.retherm.com/HowItWorks.htm
How about one that connects up to my CPU heat exchanger?
This idea has been done to death but no-one has come up with a trully affective design. Also, its only effective if you've got a cold water supply being used at the same time as draining hot water from somewhere.
The savings are difficult to quantify, and I think 40% is ambitious. I've designed something similar for a university project, and theyre quite easy to make yourself if your DIY inclined, items such as car radiators would be perfect for such an aplication
I like the idea, but how exactly are you supposed to control it?
It doesn't directly decrease the water heater usage, it just heats cold water. Personally, I always turn the hot water all the way on and leave the cold water off (my water heater sucks). Wouldn't that eliminate the usage of this thing?
Also, won't a lot of people just turn UP the cold water to cool it down rather than turn DOWN the hot? Which would also defeat the purpose, correct?
Plus, even if you do turn DOWN the hot water because the cold water is making it overall too hot, then the cold water gets colder too. I imagine the savings would be something more like 10% if you used it at maximum efficiency.
The water going down your shower's drain is likely around 100* F, the incoming water (to your hot water tank) is likely around 50*F. By piping your hot water's incoming pipe through this heat exchanger, you'll transfer a portion of that outgoing heat into the incoming water, so the temperature of the water going into your hot water tank is now ~65* F.
The hot water tank has to less hard to heat the water up to 120* F from 65* F, both increasing the length your hotwater will last and decreasing your utility bill.
Counter-current heat exchange had been used industrially for at least 50 to 60 years. It works well when there is constant flow of both streams, but does not work consumer situations because the shower is on only for 5 to 10 minutes. The heat loss by the cold pipes is one inefficiency. Another issue is the "sludge" build up. If you don't have constant flow of water to flush them out, the calcification of the soap and hair, skin etc will clog up and you'd have a hell of a time cleaning the inside of the exchanger (you can't run a snake through it).
That's quite a good point the build-up of slurry, but you can coat it with some non-stick material and add a cleanable filter before the intake I guess.
Site says:
"EcoDrain™ is installed directly in the shower drain line and features a double wall of separation between fresh and waste water to eliminate the possibility of mixing, plus an interior non-stick coating to prevent soap, hair or debris collecting inside."
So I was right about the coating.
While I like this in theory it just seems like one more thing to clog up.
It looks like they're using stainless steel construction. That's a pretty poor choice of material considering it's thermal conductivity.
Probably zinc, and inside there should be a radiator-style construction possibly made from copper, you only see the outside.
Zinc + Copper = sexy anode/cathode combination. I'd expect zinc plated copper to lose its plating very quickly.
Wow... I thought engadget had a smart reader base... but watching this thread tells me otherwise. Nay-sayers, this is really, really, really simple. go read and think for a like 10 seconds.
This is like.. a turbo for your shower.. Awesome!
As others have said, heat exchangers are nothing new. They have been around a long time... just applying them to a small scale residential use is sorta newish. That being said, this sounds like a good idea. Maybe in a few years, California will require heat exchangers in new residential/commercial construction as part of their title 24 building code standards.