THE SHORT VERSION
- A recirculation pump gets hot water to your taps faster. It doesn’t make more hot water or fix a heater that runs out.
- Controls decide the running cost. In the RESNET home energy rating method, an insulated loop running nonstop or on a timer uses about 2.4 times the water heating energy of a normal layout; a push-button demand system uses about the same as no pump at all.
- Three common setups: a dedicated return loop (best, but needs a third pipe), a crossover “comfort” valve that sends water back through the cold line (no new pipe, warm cold tap), and an on-demand pump under the sink started by a button or sensor.
- Installed cost, per HomeServe’s cost guide: about $500–$1,500 for retrofit systems that use the existing pipes and $2,000–$7,000 for a dedicated loop.
- Codes: the 2021 IRC energy provisions require controls that shut the pump off when the loop is hot and nobody needs hot water, and limit water sent into cold piping to 104°F.
What a recirculation pump does, and doesn’t do
When you open a hot tap, the water sitting in the pipe between the heater and the faucet has cooled. You run it down the drain until hot water from the heater arrives. A recirculation pump moves that cooled water back toward the heater ahead of time, or on request, so the hot water is already close to the fixture.
The wait is mostly a matter of pipe volume. EPA’s WaterSense guide lists 3/4-inch copper (type M) at 3.43 ounces of water per foot and 1/2-inch at 1.69. Say the far bathroom is 40 feet of 3/4-inch pipe and 6 feet of 1/2-inch from the heater: that is about 147 ounces, or 1.15 gallons. At 1.5 gallons a minute, a typical low-flow faucet, you wait about 46 seconds, longer if the pipe itself is cold. DOE’s Building America Solution Center notes that even in a 1,200-square-foot home the volume to the farthest fixture can exceed 1.5 gallons and the wait can top 90 seconds.
Full loops, crossover systems and on-demand pumps
Dedicated return loop
Good
- A separate pipe returns water to the heater, so the cold line stays cold
- Can serve every fixture on the loop
- Easiest to build into a new home or a gut remodel
Watch for
- Adding the return pipe to a finished house means opening walls or ceilings
- The whole loop loses heat whenever it is kept hot
Best for: New construction, remodels and long single-story homes.
Crossover (“comfort”) system
Good
- Pump at the heater, thermostatic valve under the farthest sink; no new pipe
- Grundfos says its kit installs in under an hour
Watch for
- Warm water ends up in the cold line at that sink; Watts’ manual warns of this
- Usually runs on a timer, so it keeps pipes warm whether or not anyone needs hot water
Best for: Existing homes where a routine (mornings, evenings) is predictable.
On-demand (demand-initiated) pump
Good
- Runs only after a button press, motion sensor or flow signal
- Stops when a sensor sees hot water arrive, so little heat is lost
- Meets the strictest program rules (WaterSense, DOE Zero Energy Ready Home)
Watch for
- You wait a short time after pressing the button
- Needs a button or sensor wired or paired at each area you want served
Best for: Most homes that want faster hot water without a big energy penalty.
Controls, from most to least energy
- Continuous: the pump never stops. The loop is always hot and always losing heat.
- Timer: runs during set windows. Watts’ timer works in 15-minute steps and suggests running from about 30 minutes before the first shower until 15 minutes after the last.
- Temperature (aquastat): the pump cycles to keep the loop above a set temperature, around the clock unless also on a timer.
- Demand: a button, motion sensor or flow switch starts the pump; a temperature sensor stops it. Building America’s guidance says the controls typically stop the pump after a small temperature rise, about 5°F.
- Learning or smart controls: This Old House describes self-learning units that monitor your hot water use and program themselves.
What a recirculation pump costs to run
There are two costs: the pump’s electricity, which is small, and the heat lost from pipes kept hot, which can be large. The Residential Energy Services Network (RESNET) rating method, as reproduced in a 2017 Florida Solar Energy Center report for the Florida Building Commission, scores both. The chart shows how it scales a home’s water heating energy for each type of control, assuming a typical loop length.
| Setup (R-3 insulated pipes) | Water heating energy | Extra gas a year | Pump electricity a year | Added cost a year |
|---|---|---|---|---|
| No pump (baseline) | 176 therms | — | — | — |
| Continuous or timer, 25 W pump | 2.36 × = 415 therms | 239 therms, $342 | 219 kWh, $38 | about $380 |
| Temperature control, 25 W pump | 1.97 × = 347 therms | 171 therms, $244 | 37 kWh, $6 | about $250 |
| Demand, occupancy sensor, 125 W pump | 1.07 × = 188 therms | 12 therms, $18 | 19 kWh, $3 | about $21 |
| Demand, push button, 125 W pump | 0.98 × = 172 therms | none | 13 kWh, $2 | about $0 |
Ember & Tank calculation, hypothetical home. Baseline: standard gas tank (UEF 0.63) at 55 gallons a day, 176 therms (see our operating cost guide). Multipliers (EWfact + 128) ÷ 160 and pump hours (8.76, 1.46, 0.15, 0.10 kWh per watt a year) from the RESNET method in FSEC-CR-2066-17. Pump ratings: Grundfos Comfort System UP15-10SU7P/TLC 25 W; ACT D’MAND ACT1 125 W. Prices: DOE 2025 averages, $1.43 per therm and 17.22¢ per kWh. Electric tanks and heat pumps scale the same way, so the dollar penalty for a continuous loop on an electric tank is roughly 2.4 times larger.
These are modeled figures for a rating method, not measurements in your house. Loop length, pipe size, the room the pipes run through and your hot water habits all change the result. The direction is consistent with EPA’s WaterSense guide, which says research shows timer- and temperature-based systems “can use a large amount of energy to maintain the water temperature in the recirculation loop.”
How much water it saves
Sources: EPA WaterSense, Guide for Efficient Hot Water Delivery Systems (2012); Grundfos Comfort System product sheet (2008), hosted by Young Supply.
Most of that water is clean water that cooled in the pipe, so the savings show up on your water and sewer bill. Multiply the gallons by your combined water and sewer rate per 1,000 gallons to see what it is worth where you live. A demand system also saves some energy, according to WaterSense: the water returned to the heater is warmer than water coming in from the street, and fast pumping loses less heat on the way to the fixture.
WaterSense cautions that demand systems may not suit large homes where long loops are needed, because of the energy it takes to recirculate the water in them. Overall, it says, the energy saved by not heating water that goes down the drain “typically far outweighs” the energy used to run the pump.
What codes and programs require
In homes built under the International Residential Code, recirculation is covered by the energy chapter. The 2021 IRC (section N1103.5.1, the same as IECC R403.5.1) says:
- A circulation system must use a pump; gravity and thermosyphon loops are prohibited.
- The return can be a dedicated return pipe or the cold water supply pipe.
- Controls must turn the pump off when the loop is at temperature and there is no demand for hot water, and must limit water entering cold piping to 104°F.
- Demand systems must start the pump from a user’s action, the presence of a user, or hot water flow to a fixture.
- Automatic controls, sensors and pumps must be accessible; manual controls must be readily accessible.
- Supply and return piping in circulation systems needs R-3 insulation, except cold-water-return demand systems.
Where the International Plumbing Code applies, the 2024 edition (section 607.2) caps the hot water pipe run from the source of hot water to a fixture at 50 feet and counts a recirculation loop as a source. Voluntary programs go further: EPA’s WaterSense new-home specification and DOE’s Zero Energy Ready Home program accept only demand-initiated recirculation.
Recirculation with tankless and heat pump heaters
- Tankless: a basic crossover kit may not work. Watts’ manual for its Premier system says it “does not work with Tankless water heaters.” Some tankless models build in a pump and small buffer tank; Navien’s NPE-A2 has a built-in buffer tank and recirculation pump. Navien’s warranty drops sharply for uncontrolled recirculation: heat exchanger 5 years instead of 15 and parts 3 years instead of 5 on residential installs. Ask before adding a pump to a tankless water heater.
- Heat pump: ENERGY STAR’s installer guide warns that continuous circulation strains heat pump water heaters, reducing hot water availability and raising energy use, and recommends an on-demand pump instead.
- Gas and electric tanks: work with all three types. The pump plugs into a 120-volt outlet; the Watts manual requires a grounded receptacle.
What installation costs
| Item | Range | What drives it |
|---|---|---|
| Pump and controls, equipment only | $200–$750 | Pump type, timer vs. demand controls, sensors |
| Retrofit system using existing pipes, installed | $500–$1,500 | Access under the sink, outlet near the heater, number of valves |
| Dedicated return loop, installed | $2,000–$7,000 | Pipe length, opening and patching walls, insulation, smart controls |
Source: HomeServe, “How Much Does It Cost to Install a Water Heater Recirculating Pump?” (December 22, 2025). HomeServe sells home repair plans; these are its published national ranges, not measured local prices. Electrical work for an outlet or wired sensors can add to the cost.
Crossover and under-sink kits are sold at home centers for DIY installation, and the manuals walk through it: shut off the heater’s fuel or power and the cold supply, drain the hot lines, fit the pump and the valve. The pump connection at the heater means opening the water heater’s piping, so if you aren’t comfortable with that, or the job needs a new outlet, hire a licensed plumber and electrician. For a dedicated loop, plan on a plumber. If you are replacing your heater anyway, adding a pump in the same visit is cheaper than a separate trip; see installation cost factors.
Questions for the plumber
- Which system type do you recommend for my layout, and why?
- How will the pump be controlled (button, sensor, timer), and how does it shut off?
- Will warm water reach my cold tap, and how warm?
- Is the return or loop piping insulated?
- Does my heater’s warranty or manual allow recirculation, and with what controls?
- Does this need a permit here?
Common questions
Does a hot water recirculation pump save money?
It saves water; whether it saves money depends on the controls. In the RESNET rating method, a push-button demand system uses about the same water heating energy as no pump, while an always-on insulated loop uses about 2.4 times as much.
How much electricity does a recirculation pump use?
The pump itself uses little: Grundfos rates its Comfort System pump at 25 watts, about 219 kWh a year if it never stops ($38 at 17.22¢). Demand pumps are bigger (ACT’s is 125 W) but run only minutes a day. The bigger cost is heat lost from pipes kept hot.
Why is my cold water warm after installing a recirculation pump?
Crossover systems send cooled water from the hot pipe into the cold pipe under the sink, so the first water from the cold tap there can be warm. Watts says it clears quickly. If it stays warm, check the timer isn’t set to run constantly and test the bypass valve as the manual describes.
Can I use a recirculation pump with a tankless water heater?
Only with a system the tankless maker approves. Watts says its Premier crossover system does not work with tankless heaters, and Navien shortens its warranty for uncontrolled recirculation. Some tankless units have a built-in pump and buffer tank designed for it.
Should a recirculation pump run all the time?
No. The 2021 IRC requires controls that turn the pump off when the loop is hot and nobody needs hot water, and an always-on loop has the highest energy penalty. Use demand controls, or at least a timer set to your real routine.
How long should I wait for hot water without a pump?
It depends on pipe volume and faucet flow. About 1.15 gallons of pipe at a 1.5 gpm faucet is roughly 46 seconds. WaterSense-labeled new homes must deliver hot water with no more than 0.6 gallons drawn first.
Sources
Sources checked October 5, 2026. Prices, codes and rebates change. Check current details with your installer and local permit office.
- Guide for Efficient Hot Water Delivery Systems (WaterSense new home specification, v1.1) ↗ · U.S. EPA WaterSense
- Demand plumbing (Building America Solution Center) ↗ · U.S. Department of Energy / PNNL
- Improved Hot Water Code Calculation, FSEC-CR-2066-17 (draft final report, RESNET recirculation factors) ↗ · Florida Solar Energy Center, for the Florida Building Commission
- 2021 IRC Chapter 11, Energy Efficiency (N1103.5.1 circulation systems; N1103.5.2 pipe insulation), Colorado adoption ↗ · International Code Council, via UpCodes
- 2024 IPC Chapter 6, Water Supply and Distribution (607.2), Maryland adoption ↗ · International Code Council, via UpCodes
- Hot Water Recirculation System Model 500800 installation and operation manual ↗ · Watts, hosted by Home Depot
- Grundfos Comfort System product sheet (UP15-10SU7P/TLC) ↗ · Grundfos, hosted by Young Supply
- ACT D’MAND Kontrols ACT1 submittal data ↗ · ACT, Inc., hosted by HVACQuick
- NPE-2 QuickFacts (built-in recirculation, warranty by application) ↗ · Navien
- Heat pump water heater installation guide ↗ · ENERGY STAR
- How to get hot water with a recirculating pump ↗ · This Old House
- How much does it cost to install a water heater recirculating pump? ↗ · HomeServe
- Representative average unit costs of energy (2025 prices, notice 2026-05899) ↗ · U.S. Department of Energy, Federal Register