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Quick answer from a licensed plumber: For a tank water heater with no return line, the Watts Heat H2O system is the pick: the pump plugs in at the heater and a sensor valve under the farthest sink sends cooled water back, with nothing electrical under the sink. If you already have an outlet under the sink, the APCOM UT1 does the whole job there. Neither works with a tankless heater.
Our pick for most houses: the Watts Heat H2O Hot Water Recirculation System. Check the Watts system on Amazon
A hot water recirculating pump gets hot water to a far faucet in seconds instead of running the tap for a minute. In a house without a return line, it works by sending the cooled water in the hot pipe back to the heater through the cold pipe at one sink. The two systems below do that in different places: one pump at the heater with a valve under the sink, or one pump under the sink. Which one fits comes down to where you have an outlet and what heater you have.
Recirculating Pumps Compared
| System | Pump location | Under the sink | Temperature control | Outlet needed | Warranty |
|---|---|---|---|---|---|
| Watts 0955805 | At the water heater | Sensor valve only | Valve closes at 98°F | Near the heater | 3 years |
| APCOM UT1 | Under the sink | Pump, tees and hoses | Starts below 85°F, stops at 105°F | Under the sink | Not stated in the instructions |
Figures come from the Watts and APCOM manuals and each Amazon listing. Both were listed in stock on Amazon when we checked on September 28, 2026. The Watts is sold by Amazon; the APCOM is sold by A. O. Smith Water Treatment and shipped by Amazon.
Watts Heat H2O Hot Water Recirculation System (0955805)
Pump mounts on the water heater’s hot outlet (3/4-inch) · sensor valve under the farthest sink · valve closes when the hot line reaches 98°F (listing) · built-in 24-hour timer with quarter-hour tabs · 120 V plug, grounded outlet at the heater · NSF/ANSI/CAN 61 and 372 · for tank water heaters only · 3-year limited warranty
This is the classic retrofit for a house with no return line. The pump bolts onto the hot water outlet at the heater and pushes water toward the house; a thermal sensor valve under the sink farthest from the heater lets the cooled water in the hot line cross into the cold line and flow back to the heater, then closes once hot water arrives. Watts’ listing says the valve closes when the hot side reaches 98°F. Nothing electrical goes under the sink, which is the main practical difference from the APCOM below.
Watts’ manual says to put the sensor valve at the faucet with the longest wait for hot water, and adds that a house with a branched hot line may need more than one valve, and that long or uninsulated runs may need a second valve installed in parallel. The timer lets you run it only around your peak hours. Two limits: it does not work with tankless water heaters, and the manual warns that it is not an anti-scald device and that you may get some warm water from the cold tap at that sink until it clears.
- No outlet needed under the sink; the pump plugs in at the water heater
- Programmable 24-hour timer to run it only at peak times
- Pump and valve certified to NSF/ANSI/CAN 61 and 372, per Watts
- Sold by Amazon, with a 3-year limited warranty (Watts)
- Not for tankless water heaters, per Watts
- Installing the pump means draining the hot side and breaking the heater’s outlet connection
- Warm water can come out of the cold tap at the valve sink for a moment
- Needs a grounded outlet near the water heater
Verdict: The pick for most houses with a tank heater and no return line, especially if there is no outlet under the sink you want to fix.
APCOM UT1 Under-Sink Recirculation Pump
Pump sits under the sink and ties the hot and cold stops together · built-in aquastat: starts below 85°F, stops at 105°F at the pump · built-in mechanical timer · 20–125 psi · water up to 176°F · kit: pump with bracket and 10-foot cord, 2 union sets, two 24-inch hoses, 2 tees · for tank or indirect water heaters, not tankless
The UT1 puts the whole system under the sink. Two tees go on the hot and cold angle stops, and the pump sits between them, pushing water from the hot stop into the cold stop so the cooled water in the hot line returns to the heater through the cold line. APCOM says the built-in aquastat starts the pump when the water at the pump drops below 85°F and keeps it running until 105°F reaches it, and that it typically runs three or four times an hour for one to two minutes. A mechanical timer narrows that to the hours you choose.
The trade-off is the outlet: you need a grounded 115 V outlet under the sink. APCOM’s listing says it is for homes without a return line and up to 250 feet of household piping, and for tank or indirect water heaters; its troubleshooting guide says it is not for tankless heaters. The install needs two pipe wrenches that open to 1-1/2 inches, and the hot hose has to go to the pump’s red-marked inlet side. Like the Watts, it is not an anti-scald device.
- Everything installs under the sink; no work at the water heater
- Aquastat runs it only when the line has cooled below 85°F (APCOM)
- Rated for 20 to 125 psi and water up to 176°F
- Sold by A. O. Smith Water Treatment, shipped by Amazon
- Needs a grounded outlet under the sink
- Not for tankless water heaters, per APCOM
- Warm water can come out of the cold tap at that sink
- Hose direction matters: hot to the red-marked inlet
Verdict: The pick if there is already an outlet under the sink, or you would rather not touch the water heater connections at all.
I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.
Before You Buy
- Check the heater. Both are for tank heaters; neither works with a tankless unit. For tankless options, start with our tankless water heater picks.
- Find the longest wait. The valve or pump goes at the fixture farthest from the heater along the pipe.
- Find the outlet. The Watts needs a grounded outlet near the heater; the APCOM needs one under the sink.
- Think about scalding. Both manuals say these are not anti-scald devices. APCOM recommends a thermostatic mixing valve at each point of use to limit tap temperature; see our thermostatic mixing valve guide.
- Check the stops. Old or seized angle stops under the sink should be replaced before you add a valve or pump to them.
How the Install Goes
For the Watts, turn off power or gas to the heater and close its cold supply, drain the hot side, and mount the pump on the heater’s hot outlet with the flow arrow pointing toward the house and the motor shaft horizontal, clear of any gas vent. Then fit the sensor valve between the hot and cold stops at the far sink with the supplied hoses, check it by closing the cold stop and running the cold faucet until the flow stops, and set the timer. For the APCOM, close both angle stops, add a tee to each, mount the pump with its bracket on the cabinet floor, run the hot hose to the red-marked inlet and the cold hose to the outlet, reopen the stops, and plug it in. APCOM says the system settles in 2 to 3 hours as trapped air works out.
FAQ
Do I need a return line for a hot water recirculating pump?
No, not for these two. Both use the cold water line at one sink as the return: the Watts through a sensor valve under the sink, the APCOM through the pump itself under the sink. A house with a dedicated return line can use a circulator at the heater instead.
Where should the sensor valve or under-sink pump go?
At the fixture with the longest wait for hot water, usually the one farthest from the heater. Watts says a house with a branched hot line may need more than one sensor valve, and long or uninsulated runs may need a second valve in parallel.
Why is my cold water warm after installing a recirculating pump?
Because the cold line at that sink carries the returning water. Both Watts and APCOM warn about this and say the warm water clears quickly once you run the cold tap. Neither is an anti-scald device.
Do these work with a tankless water heater?
No. Watts says its system does not work with tankless heaters, and APCOM says the UT1 is not for tankless heaters. Check your tankless heater’s manual for a recirculation mode or a model made for it.
How long does a recirculating pump run?
You set it. Both have a 24-hour timer so you can run it around mornings and evenings only. APCOM adds a thermostat: the UT1 switches on below 85°F and off at 105°F at the pump, typically three or four times an hour for one to two minutes.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber. Every size, rating, dimension and spec on this page comes from the manufacturer pages and documents listed below, which we opened and read, or from the Amazon listing we link; nothing here comes from hands-on testing. Each linked product was shipped or sold by Amazon, new and in stock, when we checked on September 28, 2026. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- Watts: Heat H2O hot water recirculation system (HWRS-WH) installation and operation manual
- APCOM: UT1 point-of-use hot water recirculation system instruction sheet
- APCOM: UT1 troubleshooting guide (PDF attached to the Amazon listing)
- Amazon listings for the Watts 0955805 and APCOM UT1 (linked above)
Bottom Line
Both systems turn the cold line at one sink into a return, so you get hot water fast without new piping. Buy the Watts if you want the pump at the heater and nothing electrical under the sink, or the APCOM UT1 if there is an outlet under the sink and you would rather not touch the heater. Put either one at the fixture with the longest wait, and skip both if you have a tankless heater.