Installing an Instant Hot Water Recirculating Pump

A hot water heating system

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A hot water recirculating pump can be used to provide instant hot water to showers and faucets when it is needed most, without wasting water down a drain as you wait for hot water to arrive from the water heater. If you have a bathroom and shower located some distance from the water heater, you may find that you need to run the shower for 30 seconds or more before the hot water from the heater flows through the pipes and reaches the shower.

With a recirculating pump installed, the water in the hot water line is constantly recirculating back to the water heater, which means that it is always warm and ready for use. There are several different designs for such systems, but the instant hot water recirculating system we'll show you here is possible to install in an existing system. 


This is not a project for beginners: The water may be extremely hot while you're completing the work, and various scenarios may arise that make completing this project difficult for those without plumbing experience. Work carefully and consider calling a professional if you encounter any issues.


Unlike some other systems, this system requires no dedicated hot water loop, and it works through means of a circulating pump installed at the water heater and a check valve installed at the sink farthest away from the water heater. The check valve is a heat-sensitive valve that circulates water back to the water heater until it is warm enough, then shuts off when the water in the hot water pipes is warm enough for use. The result is that the water in the hot water pipes is always warm when you need it, and you never have to waste water down the drain as you wait for the water to heat up.

While the recirculating pump does use a small amount of electricity, this energy cost is offset by the water you save. As an energy-saving feature, most recirculating pumps have a built-in timer that allows you to set the pump to work during the times of day when you are most likely to need hot water. You can turn off the pump at night, for example, when hot water isn't needed.

Tools and Materials

The recirculating pump kit includes most of what you'll need, including the check valve and supply tubes that are installed under the sink.

Your recirculating pump will require a 120-volt outlet to plug it in. Make sure there is an accessible outlet near the water heater. Also, depending on the configuration of the plumbing pipes at your water heater, some plumbing work and additional parts may be necessary to install the recirculating pump on the hot water exit pipe on your water heater. This is most likely when the water heater is plumbed with rigid copper piping rather than flexible tubing.


  1. Begin by shutting off the water on the shut-off valves on the cold water pipe running into the hot water heater. This valve is usually on top of the heater. Check to make sure that the flow of hot water is completely stopped by opening a hot water spigot somewhere in the house and seeing if any hot water flows. If the shut-off valve hasn't completely stopped the flow, you may need to shut off the main water supply to the house. Shut off the water heater and wait several hours for the water to cool before continuing.
  2. Disconnect the flexible water supply line on the hot side of the water heater where it goes into the water heater. Have a rag nearby to catch any residual water that will come out when the flexible pipe is disconnected. Note: You may find that these pipe connections are not flex lines, but instead are rigid pipes. If so, the process of splicing in the recirculating pump will be a little more complicated, but still possible.
  3. Screw the pump onto the hot side of the water heater. As you tighten it, make sure the timer face is turned in a direction where it can be readily adjusted. Plumber's tape can be used on the threads of the water heater nipple, but it is usually not necessary if there is a rubber gasket inside the female nut of the pump fitting.
  4. Reconnect the hot water line to the top of the recirculating pump, and tighten with channel-type pliers. You can loop the flexible line if necessary, but make sure there are no kinks that might restrict the water flow.
  5. Now go to the sink that is farthest away from the water heater to install the check valve. Shut off the water to the faucets by closing both supply valves controlling the hot and cold water supply tubes.
  6. Disconnect the faucet supply tubes from the shut-off valves under the sink. Have a towel and a container ready to catch the water that may drain out when the tubes are disconnected. Now you will connect the check valve to the faucet supply tubes.
  7. Screw the existing supply tubes coming down from the faucet tailpieces onto the top two outlets on the check valve, with the hot water line positioned on the left and the cold water line on the right.
  8. Now run the new water supply tubes from the check valve to the hot- and cold-water shut-off valves. Make sure they are connected to the correct valves. Normally, the hot water pipe will be the one on the left, and the cold water pipe will be on the right as they come out of the wall or up through the floor.
  9. With the new supply tubes tightly connected, you can mount the check valve to the wall, using the screws provided in the kit.
  10. Turn the water back on to both the sink faucet and the water heater. Run water at the far sink until all of the air is out of the lines. Check to make sure that there are no leaks at any of the connections before plugging in the power supply to the recirculating pump.
  11. Set up the pump by programming the times that you want the pump to run. The timer allows you to set operation so the pump runs when hot water is most needed.

If you ever have to shut the water off to the house, make sure and unplug the pump to avoid burning it out. The pump needs to have water circulating through it whenever it is running. Should you experience a power outage, the timer on the recirculating pump will need to be reset in order to start and stop at the proper times.