

The Ecodrain: How a simple, non-moving part can reduce hot water consumption by 40% - jskopek
http://www.inhabitat.com/2009/03/23/the-ecodrain-cuts-water-heater-use-by-40/

======
patio11
It doesn't reduce water consumption, it reduces energy consumption required to
heat water.

Now, of course, the missing calculation is how much energy is required to make
a stainless steel heat exchanger, install it, and perform maintenance. If that
is more than 40% of the energy I spend on showers over the useful life of the
device, then I'm not buying either a cost savings or an environmental
improvement, I'm buying an image of myself as "environmentally conscious".

I'll have to admit, though, if I were the manager of the gym (which has 25 hot
showers in the men's room kept between 34 and 40 degrees Celsius running for
probably in excess of 1 hour per day each), this might be pretty interesting
to me for economic reasons.

~~~
Avshalom
chances are the useful life time of a chunk of steel with a couple holes in it
is as long as the rest of your plumbing

~~~
eggnet
Being a heat exchanger I assume it uses small tubes with tight turns. Probably
not great for hair.

------
robotrout
I'm skeptical. To get meaningful energy transfer in a heat exchanger, you need
time for the two material streams to be in thermal contact with each other.
This is done by either increasing the surface areas using some porous or
tortuitous channel, or just making the channels really long. In either case,
it means you have significant pressure drop.

Now, a significant pressure drop in the incoming flow is bad enough, as I like
a strong shower. But more concerning, is the pressure drop in the drain, which
is already only at atmospheric pressure.

I predict lots of plugged drains and showers that you're wading ankle deep in
water. Or... more likely, they found all this out, reduced their pressure-
drop, and ended up with a device that doesn't really save that much energy.

------
ars
This doesn't warm up the water to the heater, but rather the water going to
the cold side of the mixing valve in the shower.

If it takes me 5 minutes to get the stupid thing at the right temperature now,
imagine what will happen when the temperature of the incoming cold water
depends on the temperature of the drain water - and it's a positive feedback -
the hotter the water, the hotter the incoming cold water, making the output
even hotter, etc.

This has the potential for using more water rather than less. Although I
assume not all faucets are as sensitive as mine - in less than a degree or so
of turning I go from freezing to boiling.

~~~
rationalbeaver
According to their actual website, you can set it up so that it feeds the
warmed water back into the water heater, rather than straight back into the
shower. Apparently there are thermostatic mixing valves that would probably
help with your problem as well (although I just read that in their FAQ and
really don't actually know what that even means).

~~~
ars
Of course you _can_ feed it that way, but the plumbing would be very
convoluted - up to the shower, through the machine, and back down to the
heater. The loss in water pressure would be bad, and can you imagine having
two showers? The plumbing would be nuts.

I know about thermostatic mixing valves, but I'd have to break the wall of the
shower, and redo all the tile. But I guess if I'm putting in this device I
could do it at the same time.

But all the thermostatic mixing values I know of actually work on water
pressure - so if someone turns on a faucet it automatically adjusts to keep
the temperature correct.

I don't know of any that actually measure the temperature of the water, which
is what is needed to help this device.

If you want to do this properly you install a heat exchanger on your main
sewer stack, and then route the incoming water line through it. They do exist,
this concept is not new.

------
mattmcknight
This line didn't add up for me: "likely your most energy-intensive daily
household activity". I think overall temperature control for my house is
vastly more expensive than this, given that my gas bill drops to $45 in the
summer but touches $300 in the winter. I also run the dishwasher every day and
do an average of one load of laundry per day (kids!).

Not a bad idea for new construction, but dialing back your hot water heater to
120F from the 140F they list probably saves more energy overall.

~~~
rationalbeaver
While I pretty much agree with you, and the water heater advice is great, I
suspect that a decent part of that $300 jump in the winter is because the
temperature of the water entering your home during the winter is much colder
than it is in the summer (a.k.a. it costs significantly more to heat the same
amount of water in the winter than it does in the summer).

~~~
HeyLaughingBoy
Probably not. Water entering the house comes in below the frost line so the
pipes don't freeze in winter and the ground temperature below the frost line
is pretty constant year-round. There is a small change, but the water coming
out of my cold faucets is almost the same temperature whether is 100F or -25F
outside.

------
Luc
I've seen an even simpler non-moving device to reduce electricity use in
supermarket freezers. Because the air in the freezer gains heat more quickly
than the produce, the freezer switches on too often. A simple sleeve for the
thermometer made in a material with heat capacity comparable to the produce
makes the thermometer measure something closer to the temperature of the food.
It got tested by the standards agency in the UK and is getting used in some
supermarket chains (I'd post a link if I could find one!).

------
yason
I'm not sure whether I like this particular design but the idea is very good
aand basic.

It is one of those things that are

\- rather orthogonal to the existing system (plumbing) \- helps a bit in each
installation \- but cumulates large gains when scaled up over a threshold
number of installations.

So far, such ideas for energy consumption haven't typically thriven largely
because energy has been cheap but this will probably change. It would be a
good idea for the government to subside installation of such devices.

In Finland (and other Nordic countries, I guess, and probably in any country
with subzero seasons) we do the same in machinated ventilation systems in
homes and buildings. The thermal energy of the warm indoors air (that is
exiting the system) is transferred to the air intake where it's used to heat
the cold outdoors air (that is entering the system).

------
devicenull
When I saw the title, I was expecting basically a low flow drain. I'd imagine
you would take a shorter shower if the water was pooling up around your feet
as you did it.

~~~
jskopek
As a previous commenter pointed out, the device purportedly saves up to 40% in
hot water energy, not consumption. My bad on the incorrect title

------
adoyle
Wastewater heat exchange is not a new concept. Here's a 1986 paper on it.
<http://www.gfxtechnology.com/Pravda.pdf>

The GFX "falling-film counterflow" system is mounted vertically, in-line with
the plumbing drain, and has a wide-bore drain pipe. It seems to me that this
is inherently less prone to clogging than the horizontally mounted Ecodrain
would be.

------
ams6110
Clever device, I'm not convinced it would save a lot of money for one person
taking a quick shower every morning, but I do think it could benefit those
households with three or four people all wanting a shower in the morning: by
recovering part of the heat from the first showers, the last person has a
better chance of getting a hot shower instead of a lukewarm or cold one.

------
bprater
Pretty brilliant in it's simplicity. I'm not sure how it'll deal with all the
crap that always works it way down the drain, though.

~~~
shawnyar217
This is from the FAQ on the EcoDrain website:

    
    
        When my drain clogs, I use chemical and/or bacterial
        cleaners to unclog it. Is it safe to use these with the
        EcoDrain?
    
        The EcoDrain is corrosion resistant and it is as safe to
        use chemical and bacterial cleaners with the EcoDrain
        as it is for the rest of the piping.
    

The FAQ also says there is a non-stick coating to help prevent buildup inside
the unit.

------
pierrefar
This doesn't add up. The drain water is, by definition, cooler than the boiler
water. Looking at the diagram, cold water is heat exchanged with the drain
water which means it will be heated but to less than what a boiler does.

This heated stream is then pumped directly to the shower to be mixed with the
boiler water, which should cool it a bit. Anyone else find this odd?

Personally I'd redesign the system to put the exchanger upstream of the boiler
water inlet which means that the boiler would need to expend less energy to
heat the water going to the shower head.

~~~
pert
The idea is that, instead of using cold water to mix with your boiler water,
you use cold water that has been slightly heated by the heat-exchanger. This
allows you to use less water from your boiler.

