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.
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?
Sometimes called a circulator pump, it is a pump that periodically circulates water back to the water heater to be reheated. There’s a clue that this is not a cost-free technique. This prevents water in the pipe from cooling off, so it is hot when you turn on the tap or shower.
The system is typically set up to circulate the water between the heater and the furthest fixture from it.
A recirculation system includes:
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). A recirculation method – 2 options. The first option is a dedicated return line for circulation. That means your home would have three pipes instead of two – cold, hot and recirculation. This is a viable option if it is installed when the plumbing is originally installed or if you have a one-story home and pipes in the basement or crawlspace are easily accessed.
If your home doesn’t have a recirculation line, then a bridge valve will be installed at the furthest fixture that allows the cold water line to be used as the means of cycling water back to the water heater.
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.
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.
Great article, answered a few questions I came with and a few I hadn’t even come up with yet. Particularly appreciate the differentiation between convenience benefits and cost benefits for different scenarios, e.g. high water cost areas, well pump applications, etc. Of note, solar electric off-grid applications typically have no/very-low water cost, shorter runs to hot taps, and higher than normal fuel costs due to delivery, so non-recirculation systems can be preferable.