Have you ever turned on a hot water faucet only to have to wait FOREVER for the water to get warm? Read this article to learn how you can get instant hot water to your kitchen and bathroom faucets.

The Problem Of Instant Hot Water

Every hot water faucet has a hot water pipe that travels from that faucet back to wherever your water heater is located in your home. In the North Dallas area where we work, the water heaters are mostly located in the garages and attics. (In older homes like those in parts of Carrollton, Richardson, southeast Plano, etc… water heaters can also frequently be found inside closets off of the main hallway in the house.)

The length of this hot water pipe determines how long it will take for hot water to get to your faucet after it leaves the tank. When not in use, the hot water cools off in the water pipes and is the first to rush out when a faucet is turned on.

If it has been hours since the faucet was last used, it could take 3 – 5 minutes before you feel hot water. That wastes a lot of water and can be quite annoying sometimes. Gallons of water can easily be wasted every time this happens.

A tankless water heater is no different, either. Tankless water heaters do not provide instant hot water to the faucets – this is a common misconception. A tankless water heater heats water instantaneously as it passes through the heater, but it can’t magically get that hot water instantly to the faucets on the other side of the house.

A picture of the distance between a water heater and hot water sink

This is the problem in a nutshell. Unless you have a mini water heater under every faucet, you can’t have instant hot water.


This is where pumps come in. What if hot water never got a chance to just sit there in the pipes and cool off? What if water flowed through all of the hot water pipes in a big loop so that it was constantly being kept nice and hot by the water heater?

This is the essential concept of the hot water recirculation pump. It keeps the water moving through the hot water system like an invisible circular bucket brigade so there will be no more water wasted down the drain and instant hot water at your faucets!

Dedicated Return Line Recirculation Pumps

There are two main categories of hot water recirculation pumps – dedicated return line pumps and retrofit crossover-style pumps.

The dedicated return line pumps are installed on a special hot water return line that is plumbed to the farthest fixture. These are usually installed when the house is built. They are often required for larger square footage homes. Otherwise, the wait time would be ludicrous.

Basically, this type of system creates a pure, simple loop in the hot water system. Hot water flows circuitously through this loop alone. The loop is designed in such a way that all of the hot water fixtures are very close to the path that it takes so there is never any substantial wait time across the whole system.

These pumps are typically installed right next to the water heaters on the return line so they are pushing water toward the water heater. Sometimes they are set to run all the time. Other times, they are set to run on a timer so that the homeowner can save a little electricity when quick hot water isn’t necessary.

A simplified illustration of how a hot water recirculation system is plumbed with a dedicated return line

Retrofit Recirculation Pump Systems

What if your house wasn’t installed with a dedicated recirculation return line? It would be a big project to go back and install a new hot water plumbing line in a house after everything has been covered up in sheetrock and trim.

Fortunately, they’ve come up with a much easier retrofit solution for just this situation! So how does it work?

The pump itself is very similar. Instead of being mounted on a hot water return line, though, it is usually mounted on the hot water outlet of the water heater. That way, it’s pushing water out of the tank and down the normal hot water pipes to the fixtures.

But wait a minute! Without a loop or some way to return the water, there would be no flow. That’s where the crossover tee comes in. Sometimes called a “bridge valve”, this ‘tee’ fitting is installed under the sink that is farthest away from the water heater. It is installed between the hot and cold pipes of the sink so that it “bridges” between the hot and cold water systems.

Now, when hot water is being pushed down the pipes by the pump, this valve allows the cooled-off water to cross over into the cold water system where it loops back to the water heater. Very ingenious! Furthermore, these valves have a mechanical wax thermostat inside them that closes when hot water reaches the fixture. That way it doesn’t put too much hot water into the cold water system.

Depending on the house floor plan, it may take more than one of the crossover valves to get hot water quickly to all of the faucets. Also, because of the way it works, there sometimes is lukewarm water that comes out of the cold side of the faucet for a few seconds when it is turned on.

There is a less-common variation of the retrofit style pump called an “on-demand” recirculation pump. This pump is mounted at the faucet instead of at the water heater. It has either a button or a sensor that turns it on so that it runs only when someone enters the room.

A simplified illustration of a hot water system with retrofit crossover style recirculation pump

Will a Recirculation Pump Save Money?

If you want to get ‘instant’ hot water or want to save water usage in your home, a recirculation pump is a great way to do that!

They can save money spent on water, but they do make the water heater work more. This is because the water heater is now keeping the entire hot system warm instead of just the water inside the tank. The larger the system is, the more heat loss occurs (which makes the water heater turn on more frequently to compensate). This decrease in efficiency and the small amount of electricity they use will offset some of the savings.

Because of these factors, the initial investment of the pump/installation, and the added cost of maintenance, a recirculation pump isn’t high on the list as a way to save money. Convenience and comfort are the main motivations when choosing to add one of these pumps to your system.

For these purposes, these pumps are highly recommended. They also tend to be very reliable as well – as long as they are manufactured by one of the larger, reputable companies like Grundfos, Taco, Etc…

What Is Involved In Installing A Retrofit Recirculation Pump?

Installing a retrofit pump or replacing a dedicated return line pump are usually pretty straightforward jobs for a plumber. The biggest variable is the soundness of the pipes that the new parts will attach to.

If the shut-off valves/supply lines/etc… are old and deteriorated, they may need to be addressed during the installation (new fixture shut-off valves, new water heater valve and supply lines, etc…).

What About Other Systems?

We covered the basics in this article, but if you are dealing with other types of systems (like with tankless water heaters) or more complicated setups (multiple hot water zones/loops) it can get more complicated. Designing and troubleshooting these setups can start to resemble designing a hydronic heating system – which is a science in and of itself. Fortunately, though, this isn’t common in your typical North Dallas residential application.

What’s Next?

Learn more about water heaters on our Water Heater FAQ Page.

Feel free to reach out if you have any recirculation-related questions. We are an award-winning gas line plumber in the north DFW area, and our reputation for integrity, craftsmanship, and upfront pricing speaks for itself.

To find out pricing and schedule availability, give us a call today at (972) 632-5412

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