What a recirculating pump does and why you might add one
A recirculating pump moves hot water from your water heater back through the supply lines and into the return line, so hot water reaches your tap faster without wasting water down the drain while you wait. Instead of running the tap for 30 seconds or a minute until hot water arrives, you get it in a few seconds. The pump sits near the water heater and connects to both the hot water supply line and a dedicated return line that runs back to the heater.
Most homes do not have a return line already installed. If yours does not, you have two choices: run a new line (which requires access to walls or crawl space) or use a point-of-use pump that mounts under a single sink and recirculates only that line. A full-home system requires more work but saves more water over time. A point-of-use system is simpler to install but works only at one location.
Before you start, check your water heater manual or the nameplate on the tank to confirm the maximum temperature the pump can handle. Most residential pumps work up to 140°F, which is standard for water heaters. If your heater runs hotter, you will need a pump rated for higher temperatures.
Key Takeaways
- A recirculating pump requires a return line from the farthest fixture back to the water heater; if one does not exist, you must run new pipe or choose a point-of-use pump instead.
- The pump mounts horizontally near the water heater, with inlet and outlet ports connected to the hot supply and return lines using compression fittings or solder.
- Most pumps run on 110-volt household current and include a timer or on-demand switch so they do not run continuously and waste energy.
- The job requires basic plumbing skills, a wrench, possibly a soldering torch if you have copper lines, and access to the space around your water heater.
- If your home lacks a return line, running one through walls or under floors is the biggest part of the installation and may require cutting into drywall or crawl space.
Checking whether you have a return line already
Walk to the farthest hot-water fixture in your home—usually a bathroom or kitchen sink far from the water heater. Look under the sink or in the wall behind it. A return line is a single pipe that runs back toward the water heater and does not carry water to any fixture; it only carries water away from the fixture and back to the heater tank.
If you see only one pipe under the sink (the supply line coming in), you do not have a return line. If you see two pipes and one of them disappears into the wall or floor without connecting to the sink itself, you likely have a return line already. Trace it if you can to confirm it runs back to the water heater area.
If no return line exists, you have two paths: install one (which may mean opening walls or accessing a crawl space) or buy a point-of-use pump that works without a dedicated return line. A point-of-use pump is easier to install but recirculates only one sink or shower, not the whole house.
Gathering tools and materials for a full-home installation
You will need the pump itself, which costs between $150 and $400 depending on flow rate and brand. Common models include the Grundfos UP series and the Taco Comfort System. Check the pump's voltage requirement—most are 110-volt, which means they plug into a standard outlet. Some require 240-volt, which needs a dedicated circuit.
For connecting the pump to existing lines, gather a wrench set (usually 1/2-inch and 3/4-inch), two compression fittings that match your pipe size, and two shutoff valves if your lines do not have them already. If your lines are copper, you will need a soldering torch, solder, and flux. If your lines are PEX or PVC, you will need the appropriate fittings for those materials.
You will also need a check valve to prevent backflow and a timer or on-demand switch (many pumps include one). A small length of flexible hose or hard pipe to connect the pump to the supply and return lines is usually necessary. Before buying anything, measure the distance from the water heater to where you plan to mount the pump and confirm the pipe size at your heater (usually 1/2-inch or 3/4-inch).
Turning off water and draining the lines
Shut off the main water supply to the house. If you do not have a main shutoff valve, locate the valve where the water line enters from the street or well. Turn it clockwise until it stops. If the valve is stuck or you are unsure, call a plumber before proceeding.
Open the lowest hot-water faucet in the house (usually a basement or laundry sink) and let the water drain. Then open a hot-water faucet on an upper floor to release air pressure and let any remaining water drip out. Leave these faucets open while you work so air can enter the lines as you disconnect them.
If you are working on copper lines, you may need to drain the entire tank. Close the cold-water inlet valve at the top of the heater, then open the drain valve at the bottom and let the tank empty into a bucket or floor drain. This takes 20 to 40 minutes depending on tank size. You do not need to drain the tank if you are working only on the supply line above the heater.
Mounting the pump and connecting supply and return lines
Position the pump horizontally near the water heater, usually on a shelf or bracket mounted to the wall. The pump must be lower than the water heater tank so gravity helps move water through it. Leave at least 6 inches of clearance on all sides for air circulation and future maintenance.
Identify the inlet port (usually marked "in") and outlet port (marked "out") on the pump. The inlet connects to the hot-water supply line coming from the heater; the outlet connects to the return line running back to the heater. If you are using compression fittings, slide the nut and ferrule onto each line, insert the fitting into the pump port, and tighten the nut with a wrench. Hand-tighten first, then give it one more quarter-turn with the wrench. Do not over-tighten, which can crack the ferrule.
If you are soldering copper lines, turn off the water supply, drain the section you are working on, and use a soldering torch to heat the fitting until solder flows smoothly into the joint. Let the joint cool for a few minutes before turning the water back on. Solder creates a permanent seal but requires practice; if you are unsure, use compression fittings instead or hire a plumber for this step.
Installing the check valve and connecting the return line
A check valve prevents hot water from flowing backward through the return line when the pump is off. Install it on the return line between the pump outlet and the water heater. Use the same connection method as you used for the pump (compression or solder). The check valve has an arrow showing the direction water should flow; make sure the arrow points toward the water heater.
The return line must run from the farthest hot-water fixture back to the water heater. If the line does not exist, you will need to run new pipe. In most homes, this means running 1/2-inch PEX or copper through the walls, under the floor, or through a crawl space. This is the most labor-intensive part of the job. If you are not comfortable cutting into walls or crawling under the house, hire a plumber for this step alone.
At the farthest fixture, the return line connects to a special tee fitting that allows water to flow back to the heater without interfering with the supply line to that fixture. The return line then runs continuously back to the heater, where it connects to a return port on the heater tank or to a special fitting on the cold-water inlet line (depending on your heater model). Check your heater manual for the correct connection point.
Wiring the pump and testing the system
Most recirculating pumps come with a power cord and plug into a standard 110-volt outlet. Position the outlet within reach of the pump—usually on the wall near the water heater. If no outlet exists nearby, hire an electrician to install one. Do not use an extension cord as a permanent solution.
Many pumps include a timer that runs the pump for 2 to 3 hours per day, usually in the morning and evening when hot water is most needed. Others have an on-demand switch that you press when you want hot water to circulate. Some models have both. Check the pump manual for how to set the timer or switch. Plug the pump in and confirm the power light comes on.
Turn the main water supply back on slowly. Open the lowest faucet again to let air out of the lines. You may hear air bubbles or see sputtering water for a minute or two—this is normal. Once water flows smoothly, close that faucet. Go to each hot-water fixture in the house and run the tap for 10 seconds to confirm hot water reaches it. If any line has no hot water, check that the return line is connected properly and the check valve is not stuck.
Checking for leaks and adjusting the thermostat
Watch the pump and all connection points for 10 minutes while the system runs. Wipe each joint with a dry cloth and look for water drips. A small drip at a compression fitting can usually be tightened another quarter-turn with a wrench. If the drip continues, turn off the water, disconnect the fitting, and reseat the ferrule or replace it with a new one.
If a soldered joint leaks, turn off the water, drain the line, and resolder the joint. If you are not confident doing this, call a plumber. A small leak now will waste water and energy over time.
Check your water heater thermostat. With a recirculating pump running, the heater may cycle on more often to maintain temperature in the lines. If your energy bill rises noticeably, lower the thermostat by 2 to 5 degrees. Most people find 120°F comfortable for daily use and still hot enough for the recirculating system to work well.
Frequently Asked Questions
Can I install a recirculating pump on a tankless water heater?
Yes, but tankless heaters are designed to heat water on demand, so a recirculating pump is less necessary. Some tankless models have a built-in recirculation mode. Check your heater manual first. If you do add an external pump, it will increase energy use because the heater will fire more often to maintain temperature in the lines.
What size pump do I need?
Most residential pumps move 3 to 5 gallons per minute, which is suitable for homes up to 3,000 square feet. Larger homes may need a pump rated for 5 to 8 gallons per minute. Check the pump specifications and compare them to the flow rate of your water heater. The pump should not exceed the heater's maximum flow rate.
Do I need a dedicated electrical circuit for the pump?
Most 110-volt pumps draw less than 5 amps and can share a standard outlet. A 240-volt pump requires a dedicated 20-amp circuit. Check the pump manual for its amperage. If you are unsure, have an electrician confirm that your outlet can handle the load.
How much water does a recirculating pump save?
A typical household wastes 10 to 20 gallons per day waiting for hot water to arrive at distant fixtures. A recirculating pump reduces this to nearly zero by keeping hot water in the lines. Over a year, this can save thousands of gallons, though the pump itself uses electricity to run. The net savings depend on your local water and energy costs.
What if I do not have space to run a return line through my walls?
A point-of-use pump mounts under a single sink and recirculates only that line without needing a return line through the house. It is easier to install but works only at one location. Alternatively, some newer systems use the cold-water line as the return path, which avoids running a new pipe but requires a special valve at the water heater.