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Conserving hot water

Like many houses, our master bathroom is at the far end of the house from the water heater.  A total of about 45 feet of copper pipe that must be heated before hot water arrives at the faucet.  This takes from 80 seconds in the summer to over 2 minutes in the winter, and wastes a lot of water and energy used to heat it.  When I learned about I learned about a clever pump made by ACT, Inc. Metlund Systems and also by Taco, I decided to install it right away.   Both systems sell for around $260 to $320.

The principle of both designs is that a pump is installed under the sink that pulls hot water up to the pump, and returns it back down the cold water pipe to the water heater at the press of a button.  The pump shuts off as soon as hot water is present.  Each time you need hot water you just press a button and wait half a minute or so before opening the faucet. 

This system differs from other designs that constantly circulate hot water through the plumbing to keep it available at all the faucets constantly.  I don't  recommend that type of system as it actually wastes energy, both at the pump and due to radiated heat loss from the plumbing which acts as a defacto radiator in the walls of your house.

The D'Mand system reduces waste and saves energy in 3 ways:

  • reduces city water supply - or well pump usage.
  • reduces the need to heat water that  would just go to waste down the drain.
  • reduces waste water to the sewer or septic system.

The only drawback is that the pump requires electricity under the sink, which requires wiring in a new (GFCI protected) outlet in most cases.


Click image for a larger version as a 320K pdf file

 Here is the complete kit:

The warm water that returns down the cold pipe is re-used as it exits the faucet rather than wasting it down the drain.
The installation of the pump is quite simple.  After shutting off the water supply and draining the lines to the sink the faucet shut offs are removed.  A tee is inserted, and the shut-off is replaced.  Then the 2 flexible lines to the pump are installed onto the new tee thread.  This took me about 20 minutes.

The kit came with tee fittings designed for compression fittings which I couldn't use, so I returned those parts and bought my own 1/2" brass tee and nipples to make the connections.  The kit also provided ribbed aluminum flex tubes, but I preferred the vinyl ones because they are easier to install, and allow the pump to be moved around as needed.  I set the pump on some 2" foam thinking that it might be noisy, but found that it is almost silent.
The challenging part that is not mentioned at all in the well written instructions is that an electric outlet is required under the sink.  The nearest outlet in our bathroom is off to the right.  So I made a run to the hardware store to get a bunch of Wiremold parts.  Then I added a breakout box on top of the existing outlet and ran Wiremold channel across and down into the space under the sink where I installed a new outlet for the pump.  This part took over 3 hours!

I also made an attractive white acrylic mount, and used my own stainless steel pushbutton rather than the standard doorbell that came with the kit.  It makes for a much more attractive installation.  Wiring this in was trivial compared to the outlet!
Once the button is pressed the pump turns on immediately and shuts off automatically as soon as it senses 120F hot water at the pump.  This saves several gallons of water that would otherwise run down the drain, and reduces the load on the water heater.  In our home the cold line returns to the bottom our solar storage tank where the sun heats it up for free.

Before the pump was installed it would take 1:20 for the hot water to arrive, now the pump brings it up in about 50 seconds after pressing the button, and the water runs hot from the faucet within a few seconds.

I later added a remote control that Metlund sell so that we can activate the pump from the downstairs bathroom as well.  They also make a motion sensor that will turn the pump on automatically when you enter the bathroom (or kitchen).