Automating your Recirculating Pump

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Save water, save gas, with this home automation project.

The shower in my house is far from the hot water heater and it used to take almost 5 minutes of running the shower before the water became hot. Fortunately, when my house was built, the hot water plumbing was run in a loop so that a recirculating pump could be installed to keep the water cycling through the pipe back to the hot water heater so that the water in the pipes stayed hot, and providing faster hot water to the faucets and shower.

This pump was already installed when I moved into the house, but running the recirculating pump all the time wasted a lot of energy, since significant heat was lost from the water as if flowed through the pipes, which are not insulated (the hot water heater is insulated). I didn't realize how much energy was being wasted until I completed the project described below. The flowing of the water back into the hot water heater was also somewhat noisy, providing added incentive not to run the pump at all times.

Many recirculating pumps come with timers so that you can set them to circulate the water before you get up in the morning, leaving them off during the day, and the back on in the evening. Typical settings will leave the pump on for about 6 hours a day.

Not wanting to leave the pump on for this long, I set the built in timer to be always on, but plugged the pump into a two way X10 appliance module (for this I used the controlled switch outlet on a RR501 transceiver module that came with my ActiveHome starter kit, but you can use a dedicated appliance module as well). I then programmed a key on each of my three KeyPadLincs (from Smarthome) to toggle the pump on and off.

The savings was amazing. During a month that the pump was on 24 hours per day (because I the timer had been accidentally disabled), my gas bill was $46. With the pump on a timer and working about 6 hours per day, my bill was about $26. After adding X10 controll for the pump my bill dropped to around $20 per month. While I am not sure that all of the difference is accounted for by this project, I think most of it was.

As set up, I find that I only need to turn on the pump about a minute or so before I need the hot water. The pump is a lot more effective at circulating the water than even opening the faucet, and using the pump doesn't waste the water (important here in California).

You can do this project cheaply, or more elaborately, as described below:

  • In the least expensive configuration you will need only an appliance module (one-way is acceptable) and a way to send X10 commands to the module, which could be with a handheld remote control unit. Some of the starter kits available meet these requirements (the appliance module might be built in to the transceiver module). This configuration will not provide an indication that the pump is on or off, but you can turn it on before you need the hot water and turn it off when you are done.
  • The main improvement in the more expensive configuration is the addition of nicer switches to control the pump from the locations where it is needed. I chose to go with the KeyPadLinc switches (three of them, one in each location). They are quite expensive, but I use the single keypad to control all of the lights in each of the rooms as well, so the cost is spread across multiple projects. If you use a KeyPadLinc, you will want to use a two-way appliance module since the KeyPadLincs will query the appliance module to verify its change in state after sending a command, and it will monitor the line for changes in state resulting from commands sent by the other switches.
One note: while I usually prefer the SmartHome modules to the X10 modules, in this case I do not recommend using the SmartHome ApplianceLinc module, since at least for the two way version that I have, the device occasionally locks up and requires me to unplug it and plug it back in. Since the module is in the garage, behind the water heater, this would not be very convenient. I do, however, highly recommend the KeypadLinc switches from SmartHome to send commands to the module.