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Here is my drainwater heat exchanger installation page.

Finally I have finished my drainwater heat exchanger installation. I had thought of the idea of recovering heat from the shower water about 7 years ago knowing it takes a lot of energy to heat water. I talked about it with a couple of the guys I work with and all agreed it would be a good idea. I came up with a method but we saw problems with that both technical and building code wise.

Then my coworker went to a plumbing trade show and got some literature on a product that did this in a much better fashion than I had envisioned. The exchanger is made up of a 4" copper drainpipe with ½" copper water pipe wrapped around the entire length except for a short space at the ends for attaching it to the sewer line. It is inert, requires no maintenance and has no moving parts to fail so it should last a really long time.

The unit is mounted vertical so when drainwater enters the 4" inside pipe it spreads out around the inside of the pipe to transfer as much heat as possible to the 4" pipe and then to the ½" pipe and to the water going through the ½" pipe. It looked very interesting.

When I moved into my new house we had well and cesspool but I knew water and sewer were coming soon. I purchased one of these exchangers so that when I had my water and sewer installed I could have the plumber install it in the sewer pipe since it would be apart anyway. That took care of the dirty end of the installation.

Along with the rest of the installation I wanted to move the water heater from where it was currently located in the middle of the basement against the far wall as far away as it could get from everything that uses it to right under the bathrooms next to the exchanger to shorten the pipe length to the bathrooms to avoid wasted water and energy. I figured I would just take my lumps with the kitchen, which is located at the other end of the house. There are only two of us and we only need the hot water in the kitchen for the dishwasher, which we only run once a week as opposed to the bathrooms, which we use, everyday.

During the install I also wanted to cut the plumbing for the two bathrooms apart and install valves so I could shut down one bathroom and work on it without affecting the other. Previously, there was a set of valves for that entire end of the house. The rest of the install including moving the water heater and cutting apart the bathrooms and adding the valves took about 5 hours. If you were simply installing the exchanger it could probably be done in about 2 hours.

The model I chose is supposed to recover 56% of the heat in the drainwater that would normally go down the drain and use it to preheat the water going into the water heater so it doesn't have to heat the water from dead cold.

I have measured the following results:
Drainwater enters the unit at about 80 degrees from a shower for example. I can't measure the drainwater temperature coming out the bottom of the exchanger because there is no place for me to attach a sensor but I can guess it is not colder than the incoming water in the ½" pipe.

Water enters the house at 50 degrees. It goes through the water softener tank and on to the exchanger where it enters the exchanger at about 53.5 degrees. It exits the exchanger and heads to the water heater at 70 degrees for a 16.5 degree gain and leaves the water heater at 100 degrees for a 30 degree gain. The total heat rise is 46.5 degrees with 16.5 degrees or about 36% of the rise coming from the exchanger.

I guestimate I use about 150KWH/month to heat water so at 36% provided buy the exchanger my savings should be around 54KWH/month or about 1/8th of my total household electricity usage. This also amounts to about 1/2 ton of CO2/year not expelled into the environment.

A rough guess seems to indicate that the unit is performing as advertised. I will have to wait for the electric bill after this one to get a full month with the exchanger installed to see how it is really doing.

My goal in doing this is to reduce the amount of power I have to generate in order to get closer to going off grid and providing for myself completely. Of course, if every household in the country were to install one of these we could probably eliminate the need for quite a pile of new coal fired electric plants or at least a couple of nuclear plants and give a big break to our aging electrical infrastructure.

If you are using natural gas or propane this will probably result in a fair amount of savings also not to mention the environmental aspects and the ability to go longer between propane refills.

The other good thing about this device is it enables the water heater to recover faster because it is not heating water up from dead cold thus allowing more showers in succession if needed or in the case of alternate energy, less energy required in general to heat the water maybe allowing the use of 12 volt water heater coils or allowing a solar water heater to provide more hot water.

Since it recovers a percentage of the heat normally lost, the more hot water your family uses the more your savings will be. Again, there is only the two of us in my house so a larger family will save more. As far as I am concerned, this device should be installed in all new construction without question and should be seriously considered for retrofit into all houses, laundries, hair salons, restaurants and any public building supported by taxes such as schools, government buildings and so forth. So far I am pleased with the performance of this unit.

Drainwater heat exchanger

I decided to make a "hat" for the top of my water heater. This one is crude but I will probably make it round and tape the water heater insulation right to it instead of the top of the water heater.

Here is where I got it.

Swing Green Drainwater heat exchanger

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