Best Tankless Water Heaters With a Recirculating Pump
The fix for the one tankless complaint that arrives in week two: the wait at the far bathroom.
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If you have no dedicated return line, the Rinnai RSC199iN is the pick: ThermaCirc360 recirculates through the cold supply instead, which turns a re-pipe into a straightforward install. If you have long runs and short repeated draws, the Navien NPE-240A2 adds a buffer tank as well as a pump.
Tankless units only start heating when water flows. So at a distant fixture you wait for the cold water in the pipe to clear, plus a second or two for ignition. In a large house that can be 30 to 60 seconds and several gallons down the drain, and it is the number one complaint from new tankless owners.
Recirculation fixes it by keeping hot water moving in the pipe so that when you open the tap, hot water is already close by. There are two ways to do it and they suit different houses.
The two approaches
| Built into the heater | Separate comfort pump | |
|---|---|---|
| Where the pump lives | Inside the heater cabinet | Under the furthest sink, or at the heater |
| Needs a return line? | Not with ThermaCirc360 or NaviCirc | Not with a crossover valve |
| Control | The heater's own controller and schedule | Built-in timer, or a push button, or a motion sensor |
| Cost | Built into the unit price | Separate purchase, far cheaper than the unit difference |
| Serviceability | One more part inside the heater | Replaceable on its own |
| Best for | New installs and whole-house retrofits | Adding comfort to a heater you already own |
Quick picks
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| # | Product | Best for | Price |
|---|---|---|---|
| 1 |  Rinnai SE+ RSC199iNThe pick when you want hot water fast at a far bathroom and have no dedicated return line: ThermaCirc360 recirculates through the cold line instead, and the 15-year heat exchanger warranty is the longest here. | Recirculation without a return line | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 2 |  Navien NPE-240A2The high-flow pick: 11.2 GPM and a built-in buffer tank plus recirculation pump, which is what stops the cold-water sandwich on short, repeated draws. | Big draws and long pipe runs | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 3 | Grundfos UP15-10SU7P Comfort SystemThe comfort-system pump that made under-sink recirculation normal: 25 watts, a built-in timer and a line cord, in a stainless body rated to 150°F. | Recirculation with no return line | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 4 |  Rheem Prestige RTGH-95DVLNThe condensing gas tankless most houses should start with: 5.5 GPM at a 70°F rise covers two showers in a cold-inlet climate, and the 12-year residential heat exchanger warranty is the longest on this list. | Most whole-house gas jobs | Check price on Amazon No live price feed on this site, so we show none. #ad |
The picks in full
Pick 1 — Recirculation without a return line
Rinnai SE+ RSC199iN
The pick when you want hot water fast at a far bathroom and have no dedicated return line: ThermaCirc360 recirculates through the cold line instead, and the 15-year heat exchanger warranty is the longest here.
| Fuel | Natural gas |
|---|---|
| Gas input | 199,000 BTU/h |
| Maximum flow | 11 GPM |
| Efficiency | 0.95 UEF |
| Installation | Indoor only |
| Recirculation | ThermaCirc360 — works with or without a dedicated return line |
| Warranty | 15-year heat exchanger, 5-year parts, 1-year labor |
What is good
- Built-in recirculation means no separate pump, timer or control to buy and wire
- ThermaCirc360 can use the cold supply as the return, which is the difference between a half-day job and a re-pipe
- 15-year heat exchanger warranty
- 0.95 UEF keeps it inside most utility rebate thresholds
What is not
- Indoor installation only — no outdoor variant of this exact model
- Natural gas only in this model number
- Crossover recirculation through the cold line puts warm water in the cold tap for a few seconds
Skip it if: Skip it if you are plumbing a new build where a dedicated return line is going in anyway. You would be paying for the integrated pump twice over, and a plain condensing unit plus a separate pump is cheaper and easier to service.
No live price feed on this site, so we show none. #ad
Specifications above from Rinnai RSC199iN product page. We have not tested this unit ourselves.
Pick 2 — Big draws and long pipe runs
Navien NPE-240A2
The high-flow pick: 11.2 GPM and a built-in buffer tank plus recirculation pump, which is what stops the cold-water sandwich on short, repeated draws.
| Fuel | Natural gas or propane |
|---|---|
| Heat input range | 13,300 - 199,900 BTU/h |
| Maximum flow | 11.2 GPM |
| Efficiency | 0.95 UEF |
| Recirculation | ComfortFlow built-in buffer tank and recirculation pump |
| Heat exchanger | Dual stainless steel |
| Venting | 2-inch PVC |
| Gas connection | 1/2 inch |
What is good
- The buffer tank is the real feature — it smooths the short draws that make other tankless units run cold for a second
- NaviCirc lets it recirculate through existing supply lines with no separate return
- 13,300 BTU/h minimum fire means it modulates very low for a single faucet
- 2-inch PVC venting and a 1/2-inch gas connection make retrofits easier than the headline BTU suggests
What is not
- More internal parts than a plain condensing unit: a pump and a buffer tank are two more things to service
- Warranty terms are not published on the quick-facts sheet — check the current warranty document before you buy
- Condensate drain required
Skip it if: Skip it if you are replacing a single-bathroom apartment's heater. The buffer tank and pump are solving a problem a small home does not have, and you would be paying for both.
No live price feed on this site, so we show none. #ad
Specifications above from Navien NPE-2 series quick facts (PDF); Navien NPE-A2 series technical data. We have not tested this unit ourselves.
Pick 3 — Recirculation with no return line
Grundfos UP15-10SU7P Comfort System
The comfort-system pump that made under-sink recirculation normal: 25 watts, a built-in timer and a line cord, in a stainless body rated to 150°F.
| Power | 25 W |
|---|---|
| Voltage | 115 V, 0.23 A, single phase |
| Motor | 1/25 HP |
| Flow range | 0 - 6.3 GPM |
| Head range | 0 - 5.1 ft |
| Maximum pressure | 145 psi |
| Temperature range | 36 - 150°F |
| Body | Stainless steel |
| Connections | 3/4 in female NPT inlet, 3/4 in male NPT outlet |
| Controls | Built-in timer and line cord |
What is good
- 25 watts is less than the light bulb it is usually compared to
- Built-in timer means it only runs when you want hot water, not all day
- Stainless body is the right choice on the potable side
- Line cord: it plugs in rather than needing a wired connection
What is not
- 5.1 ft of head is modest — long or tall runs need a bigger pump
- A crossover-valve install puts warm water in the cold line at the far fixture
- 150°F maximum rules out tanks set higher for Legionella control
Skip it if: Skip it if your tank is set above 150°F for scald-control-plus-mixing-valve reasons. The pump's temperature limit is a hard limit, and a comfort pump cooked by 160°F water is a warranty conversation you will lose.
No live price feed on this site, so we show none. #ad
Specifications above from Supply House listing, Grundfos 99452459 UP15-10SU7P; Grundfos Comfort System and Alpha pump data. We have not tested this unit ourselves.
Pick 4 — Most whole-house gas jobs
Rheem Prestige RTGH-95DVLN
The condensing gas tankless most houses should start with: 5.5 GPM at a 70°F rise covers two showers in a cold-inlet climate, and the 12-year residential heat exchanger warranty is the longest on this list.
| Fuel | Natural gas (LP variant sold separately) |
|---|---|
| Gas input | Up to 199,900 BTU/h |
| Flow at a 70°F rise | 5.5 GPM |
| Maximum flow | 9.5 GPM at a 35°F rise |
| Efficiency | Up to 0.93 UEF, stainless condensing heat exchanger |
| Minimum activation flow | 0.4 GPM |
| Venting | Up to 150 ft of 3-inch PVC; 60 ft of 2-inch PVC |
| Dimensions | 18-1/2 in W x 9-3/4 in D x 27-1/2 in H |
| Warranty | 12-year heat exchanger (residential), 5-year parts, 1-year labor |
What is good
- The 70°F-rise figure is published, so you can size it honestly instead of guessing from the headline number
- Condensing design vents in PVC, which is far cheaper to run than stainless category III pipe
- 0.4 GPM activation means a trickle at a bathroom faucet still fires the burner
- Long PVC vent runs let you put it where the gas line already is
What is not
- Needs a gas line sized for nearly 200,000 BTU/h — many existing 1/2-inch runs are not
- Condensate has to go somewhere, which means a drain or a condensate pump
- Annual descaling is not optional on hard water
Skip it if: Skip it if your gas meter and line cannot carry 199,900 BTU/h. Upsizing the gas line is often the single largest cost in a tankless conversion, and no amount of unit quality fixes a starved burner.
No live price feed on this site, so we show none. #ad
Specifications above from Rheem RTGH series specification sheet (PDF); Pace Supply listing, RTGH-95DVLN, 199 kBtu/hr. We have not tested this unit ourselves.
The crossover trade-off, stated honestly
Recirculating without a dedicated return line means using the cold supply as the return path. That works, and it is why these systems are retrofit-friendly. The trade is that for a short while after the pump runs, the cold tap at the far fixture delivers warm water.
For most households that is a minor annoyance in exchange for not re-piping the house. For a household that cares about genuinely cold drinking water at the kitchen tap, it is worth knowing before you install rather than after.
Do not run it continuously
A recirculation system running 24 hours a day converts the one efficiency advantage of tankless — no standby loss — into a continuous loss through the pipework. Every sensible configuration is scheduled or on demand:
- A timer covering the morning and evening windows. The Grundfos Comfort System has one built in and the pump draws 25 watts.
- On-demand, via a push button at the fixture or a motion sensor in the bathroom, which only runs the pump when someone is actually about to use water.
- The heater's own learning schedule, where the unit observes usage patterns and pre-heats accordingly.
What goes in with it
A water heater is a system, not a box. These are the parts that go in with it, and the ones people discover they need halfway through the job.
- Flush kit
The annual descale is not optional on a tankless unit, and you need a pump, hoses and a bucket.
- Descaler solution
What actually dissolves the scale once the kit is hooked up.
- Recirculation pump
Fixes the cold-water delay that makes new tankless owners call a plumber.
How we chose
We ranked on whether the system works without a return line, how it is controlled, and whether the unit also addresses the cold-water sandwich. We have not tested these units. How we pick.