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A recirculation pump brings hot water to your faucets in seconds instead of minutes. Here is how it works with a tankless water heater.
Without recirculation, the water sitting in the pipes cools down between uses. When you open a hot tap far from the heater, you wait for that cold water to clear, often 30 seconds to a couple of minutes, wasting gallons each time. A tankless water heater recirculation pump keeps a loop of hot water moving so it is near the faucet when you need it.
A tankless water heater circulation pump, also called a recirculating pump for tankless water heater systems or a recirc pump for tankless water heater setups, solves this. Installing a tankless water heater with recirculating pump control is one of the best upgrades for larger homes.
| Built-in recirculation | External pump | |
|---|---|---|
| Setup | Pump and controls inside the heater | Separate pump on the plumbing |
| Control | Integrated schedules, app or on-demand | Pump timer, aquastat or on-demand switch |
| Compatibility | Designed for the unit | Must be approved by the heater manufacturer |
| Examples | Rinnai Sensei RXP, Navien NPE-A2 | Small circulator with timer or demand controls |
Navien’s A2 models include a small buffer tank and pump, which also smooths out cold-water sandwich effects.
For example, a Rinnai tankless recirculation pump can be built in (RXP models) or external, as approved by Rinnai.
Check whether your tankless model supports crossover systems; some require a dedicated return.
For a single far bathroom, a point-of-use water heater at that sink can be cheaper than a recirculation system. See our point-of-use guide.
Look for "recirculation" in the features of whole-house units.
Yes, if the manufacturer allows it. Many tankless models are designed for recirculation, either with a built-in pump or an approved external pump and control settings. Using an unapproved setup can cause short-cycling or error codes.
Continuous recirculation wastes energy by keeping pipes hot all the time. Timer, temperature-controlled or on-demand (push-button or motion) controls cut the waste dramatically.
Not always. A dedicated return line works best, but crossover-valve systems use the cold water line as the return, which is easier to retrofit. Some tankless brands require a dedicated return line for their built-in pumps.
Some do. Rinnai’s Sensei RXP models include a built-in recirculation pump, while other Rinnai models work with an approved external pump. Check the model’s specifications.
This guide is general information for U.S. homeowners, not professional advice. Gas, electrical and venting work must follow the manufacturer’s instructions and local codes, and in most areas requires a licensed plumber, electrician or gas fitter and a permit. Specifications and prices change; always confirm details on the product page and in the installation manual.
