Stop Energy Going Down the Drain
Here are three of the DWHR devices tested, showing the
headers: Left to right, the Retherm S3-60, GFX G3-60,
and PowerPipe S3-60. Credit: Charles ZaloumI don't think there is one big solution to our energy problems and the environmental problems related to the use of fossil fuels–there are lots of little solutions that in the end add up to a big solution.One of those little solutions I have been reading a lot about lately is a Drain Water Heat Recovery Device (DWHR). It looks like part of something you would find hidden in the hills and hollows of Appalachia that makes moonshine, but a DWHR device is a simple copper coil that you put around your shower drain that recovers some of the heat from your shower water. Cold water is circulated through the coils, gets heated by the drain water, and then flows into your hot water tank, or into your shower and hot water tank.The device is simple, effective, and doesn’t require much (like, no) maintenance. Drain water heat recovery devices contribute to large energy savings in laundries and in multifamily buildings, but will also work very well in single-family homes–as long as there is room under the showers. My one-story house in Walnut Creek is not a good candidate for such a device.
The simple workings of a drain water heat recovery device.
Credit: gfxstar.ca, Inventroment Energy Solutions.Canadian researchers from Natural Resources Canada tested the effectiveness of several DWHR devices at the Canadian Centre for Housing Technology. For an Ottawa household in which four people each take 12 minutes showers every day, a DWHR will save $150 a year in energy costs (at present, Canadian dollars are about equivalent to U.S. dollars). That's about three times as much energy saved as the energy used to run an energy-efficient 20-cubic-foot refrigerator for a year. Over the 30-year lifetime of the DHWR, which costs about $800 including installation, the device will save the household close to $3,000.The Canadian researchers created a Web-based Drain Water Heat Recovery-Energy Savings Calculator where building contractors, plumbers, and homeowners can go to estimate the cost effectiveness of several DWHR devices on the market. You just need to know the model of the device, the temperature of your shower water, estimated shower times, and so on. Right now it is set to work for Canadian locations. For U.S. homeowners, you have to pick a city in Canada. The calculator will be updated as newer technology is developed and tested.
Here are some Web sites where you can find out more about DWHR devices that were submitted for testing at the Canadian Centre for Housing Technology:
- Power Pipe www.renewability.com
- ECO-GFX www.gfxstar.ca
- Retherm www.retherm.com
If a million households in the United States installed DWHR devices, we’d save a collective $150 million in annual energy costs, or about the equivalent of 1.25-billion kWh of electricity–or a ginormous amount of carbon dioxide in air from the natural gas not burned and electricity not generated.
Jim Gunshinan is Managing Editor of Home Energy Magazine. He holds an M.S. in Bioengineering from Pennsylvania State University, State College, Pennsylvania, and a Master of Divinity (MDiv) degree from University of Notre Dame.
6 Comments
I believe that people should approach these particular devices with quite a bit of skepticism.
I don't mean to say that recovering heat from a single heavily-used shower would not be useful, but supplier claims such as "WILL SAVE YOU UP TO 50% ON YOUR HOT WATER BILL" seem exaggerated. It would be more effective and a lot cheaper to install a simple cutoff valve by the shower head and reduce the water run time during those 12-minute showers to 6.
To achieve 50% heat recovery would require most of your hot water to pass through the recovery device. The counterflow heat exchanger designs shown are good, but 100% efficiency is not possible. Effectiveness would be reduced any time cold water is used at the same time, reducing the temperature difference at the exchanger. Little or no heat would be recovered during short-duration uses of hot water. A choice must be made between an exchanger located at the most-used shower, sacrificing recovery from water used elsewhere, or redesigned sewage piping with some heat lost between the source fixtures and the heat exchanger. Again, nothing against the approach, but be careful of the claims.
Steve,
I reported on the study done by researchers at Natural Resources Canada. I believe their results, but, like you, feel very skeptical about "50% energy savings" claims.
The Canada researchers found that that shower was the big saver, compared to other uses. I will forward your comments to the authors of the report though.
Thanks for you thoughtful comments.
Steve,
I forwarded your comments to Charles Zaloum, one of the authors of the Canadian DWHR study. Here is his response:
"Manufacturers love using "save UP TO 50%"….I'm still waiting for my vehicle to get the posted gas-mileage!
Our research has shown that, even with the best DWHR device, your standard family will save 25-30% on the hot water portion of their utility bill. Of course, if you have 4 teenagers, you'll be saving closer to 40-50%….since your hot water use is dominated by shower use.
Agreed, reducing (as with garbage, and energy) is Step 1…the cut-off valve is probably the most cost effective measure.
Step 2 is re-use…some "enviro-homes" now re-use filtered shower water to flush toilets… Step 3 is recycle, as in recycle (or recover) energy that would normally be wasted.
The problem with this beautiful theory is PEOPLE. PEOPLE need to decide to reduce their hot water use…PEOPLE need to decide to use the cut-off valve….I could train by horse to talk before I could train a teenager to take a 5-minute shower or use a cut-off valve!
The DWHR deals with the PEOPLE-factor by being invisible, simple and effective….PEOPLE, it would appear, don't like to put much effort in conserving energy…"
[...] Stop Energy Going Down the Drain [...]
Save up to 50% means that in the perfect case scenario, you will save 50% on your hot water bill. As Charles points out, this is in a perfect situation. The best way to calculate savings is by
1) Knowing the price of the heat exchanger and
2) Visiting the website that uses a calculator developed from the NRC testing to see what your particular payback would be.
http://www.ceati.com/calculator/
If you have any more questions on drain water heat recovery devices, I am free to answer them. We are the manufactures of the ECO-GFX
Daniel Beauchemin
daniel.beauchemin@gfxstar.ca
Eco-Innovation
888-881-7693
Correction: The diagram in my blog entry "Stop Energy Going Down the Drain," should have been credited to Carmine Vasile, who invented the original drain water heat recovery device, the GFX, in the 1990s. I regret the error. Vitale is the president of WaterFilm Energy, Inc. Go to http://www.gfxtechnology.com for more information about the GFX.