Tankless Water Heater: Is a Recirculating Pump Worth the Money?

The beauty of a whole-house tankless water heater is that you don’t have heated water cooling off in a tank, only to be reheated again whether or not its used.

That’s a pro.

Here’s a con – at least when comparing whole-house units to a point of use tankless unit installed at the sink: The hot water is still a long way from many taps, and it takes a long time for the water to warm up.

Wasted time.

Wasted money, as water you’re paying for (if metered) runs down the drain. One homeowner suggested catching the water in a bucket while waiting for it to warm up and using it to water garden plants.

Why Does Hot Water Take So Long to Arrive?

When you have a traditional tankless system and open a faucet, cold or lukewarm water in the pipes must be pushed out by heated water from the tankless unit. If the water heater is on the other side of the house—or even just a few rooms away—this can take 30 to 90 seconds or longer. While the water eventually gets hot, waiting wastes time and causes unnecessary water usage if you let it run down the drain.

Factors that can slow down hot water arrival include:

• Length of plumbing runs: The longer the distance between the water heater and a fixture, the longer you’ll wait.
• Pipe material and diameter: Larger or older pipes hold more water that has to be flushed out before hot water arrives.
• System flow rate: Tankless water heaters typically need a certain flow rate to activate. If you’re drawing less water than required, the heater can be slow to engage.

Here’s a better solution: A recirculating pump that keeps heated water in the tap and instantly available at the sink or shower.

Here’s a fuller recirculation pump explanation of how it works plus its cost, pros and cons.

What is a Recirculation Pump for a Tankless System?

A recirculation pump (also called a circulator pump) cycles water back to the heater periodically or on demand. This prevents the water in the pipes from fully cooling down, ensuring you get hot water almost immediately when you turn on the tap or shower.

Key Points:

• Periodic pumping: The system can run on a schedule or respond to a temperature sensor, turning on only when water in the line falls below a certain temperature.
• Minimized wait time: Because the water in the hot line is kept warm, there’s no need to wait for cold water to purge out of the pipes.

Systems & Components: A Quick Overview

A recirculation system typically includes three main elements:

1). A water heater and pump combined or separate. This can be a tankless water heater with an integrated recirculation pump or a water heater and an external pump. The Rheem RTGH is one of example of a unit with a built-in recirculation pump.

Other models, like the Rinnai RL water heaters, can be programmed to start an external pump during peak water usage times.

2). Recirculation method – 2 options.

• Dedicated Return Line: A separate plumbing line that returns unused hot water to the heater. This is easier to install if your home is being built or remodeled, or if you have accessible plumbing (e.g., in a basement or crawlspace).
• Bridge Valve: If there’s no dedicated return line, a bridge valve can be installed at the fixture farthest from the heater. It uses the cold line for water return, eliminating the need for extra piping.

3). A way to control when the circulation pump runs. The two common options are a timer that periodically turns on the recirculation and an aquastat or thermostat that turns on the pump to keep water in the line at the desired temperature.

Many recirculator pumps have a built-in aquastat or timer.

If you’re still wondering what a recirculation system does, here’s a helpful video from This Old House. It shows a tank-style water heater, but the way the system works is the same.

Cost, Pros & Cons of Recirculation

There are important considerations before deciding to add recirculation technology to your tankless water system setup.

Cost

• Tankless heaters with recirculation pumps: The cost is $250 to $415 more than those without pumps. This is the best choice if you’re installing a new water heater. It saves the cost of pump installation.
• Separate recirculation pumps: If you have a tankless unit without a pump, one can be installed. Pumps cost $235-$400 depending on the size required. Some can be DIY installed. If you pay a plumber to do it, installation cost will be $125 to $300.
• Complete kits: If you’re not installing a separate recirculation pipe, then a bridge valve can be installed. Separately, they cost about $25. They are also available in complete kits with the pump and aquastat. Kits cost $260 to $450.
• Recirculation line: If the line is installed when the other plumbing is installed, the cost is $75 to $300 based on the length of the line. When the line is installed later, cost can exceed $1,000.

Advantages of Recirculation

Convenience: This is the only proven advantage. You don’t have to wait a minute or two, sometimes longer, for hot water to reach the tap, shower head or clothes washer. 

Potential cost savings: Some readers are thinking, “Wait a minute. How does this save money? The unit is running more often, burning fuel, and that is a cost, not a savings.”

That’s exactly right.

If you have a well, the only energy being used during the time it takes for hot water to reach the tap is a little bit of electricity to run the pump. Recirculation technology will cost you money for the convenience it provides.

If you have very expensive metered water (think California or Arizona), then might save more money on your water bill than you’ll spend on gas to fire the water heater during recirculation.

Many sellers encourage recirculation technology in the name of conservancy. The water you save is offset by the fuel you burn.

Disadvantages of Recirculation

System and installation cost: You’ll pay $300 to more than $2,000 for the equipment, pipe and installation, depending on what equipment you buy and who installs it.

Operating cost:  As we’ve said, for many homeowners, the cost in natural gas or propane will be higher than the savings from using less water.

Environmental Considerations: Water vs. Energy

There’s a balancing act between conserving water and using more energy:

• Water Conservation: In drought-prone or high-water-cost areas (e.g., parts of California or Arizona), every gallon saved is valuable. If your water rates are steep, recirculation can trim your monthly bill.
• Energy Footprint: Recirculation pumps require electricity to run, and your tankless heater will fire more often to maintain water temperature. If saving energy is your top priority, you might consider on-demand recirculation systems that only activate when you need hot water (e.g., with a button or motion sensor).

Ultimately, it’s worth comparing the cost of water in your area against the extra fuel you’ll burn by running a recirculation system.

Who Benefits Most from Recirculation?

1. Homes with Long Plumbing Runs
   If your shower or kitchen sink is on the opposite side of the house from your water heater, you’ve probably stood there watching cold water run down the drain while waiting for it to heat up. A recirculating pump sends hot water through the pipes more frequently, meaning you don’t waste time—or water—waiting.

2. High Water Cost Regions
   If you pay dearly for water—think parts of California or Arizona—then a recirculation system might actually save you money by cutting down on wasted water. Yes, you’ll spend a little more on energy to keep it hot, but that extra cost can be offset if your water rates are sky-high.

3. Those Seeking Maximum Convenience
   Some folks just can’t stand waiting for the water to warm up, especially first thing in the morning or late at night. A recirculation pump keeps hot water readily available at the tap or shower head. If instant comfort is a priority, this setup is a no-brainer.

FAQ: Common Questions About Recirculation

Q: Can I add a recirculating pump to my existing tankless heater?
A: Generally, yes. If your tankless heater doesn’t have a built-in pump, you can install an external one. Just be sure your specific model is compatible with the pump and any controls (like timers or aquastats) you plan to use.

Q: Will a bridge valve affect my cold water supply?
A: Bridge or crossover valves send a trickle of warm water into the cold line so it can flow back to the heater. You might notice that your cold water isn’t quite as cold at times. But with proper settings on the pump and aquastat, most homeowners say it’s barely noticeable.

Q: Do recirculation pumps make noise?
A: Most modern pumps run quietly. If you do hear loud rattling or humming, it might be an installation or maintenance issue. A quick inspection—or a call to your plumber—should clear things up.

Q: Are there any tax incentives or rebates for recirculation systems?
A: This varies by region. Some cities or utilities provide rebates for water-saving measures, which can include recirculation pumps. Check with your local water or energy provider to see what’s offered in your area.

Is a Tankless Water Heater Recirculation Pump Worth the Money?

That’s the question we started with.

Now you know the facts.

Only you can answer the question. For most homeowners that say “yes,” the reason is convenience they are willing to pay for.  We also published a post discussing the best recirculation pump for DIYers and you can check this article if you are interested in installing a recirculation pump for water heater.

For a small percentage with high water costs, the system will eventually pay for itself and then create cost savings going forward.