Hot Water Recirculating Pumps
Get Instant Hot Water
During my home inspections, waiting for hot water at the shower is one of the chief complaints from new home buyers. Fortunately, this common house malady is easily remedied by installing a hot water recirculating pump.
These recirculating pumps are installed either above the water heater (coupled with a sensor valve) or installed under a sink as an all-in-one unit.
In this guide, I will go over…
- Recirculating systems installed above the water heater
- How exactly hot water recirculating pumps work
- All-in-one recirculating water pumps installed under the sink
- How to install hot water recirculating pumps
- Single shower tankless, mini tank, and shower head heaters
What's In This Guide?
Hot water recirculating pumps are a simple solution to the problem of waiting for hot water at a sink or shower.
The standard installation is a small water pump above the water heater, and a sensor valve that is installed under the farthest sink.
Hot water recirculators can be installed in under two hours if all you have to do is change out the flexible threaded piping to the water heater.
However, if you have copper or CPVC to the water heater, then the installation may require a qualified plumber. The total costs for a hot water recirculation system will usually be in the $250 to $750 range which includes the pump and labor.
The average household wastes over 10,000 gallons of water a year. These recirculators can save a significant amount of water over a year. In fact, some cities even have rebate programs for homeowners who install hot water recirculation systems.
These water pumps are also usually used in tandem with timers. You can set the timers to turn the pump on during peak water usage such as in the morning and evening.
Here is my detailed review on the best rated hot water recirculating pumps!
In my opinion, hot water recirculators are the best way to get instant hot water to a shower, bathroom, or sink.
But of course, there are a some pros and cons that come with buying these specialized water pumps.
I think you know the biggest pro (instant hot water for the whole house) but not many people realize that one con is that sometimes you may have to wait 3 to 9 seconds to get cold water.
That’s because for retrofit installs (homes without dedicated hot water returns), the recirculator will temporarily use the cold water supply line as a temporary return back to the water heater. So if you need cold water for whatever reason, and you haven’t been home for a while — you will probably get lukewarm water for a few seconds.
And besides instant hot water, a large advantage of recirculators is how they save water. According to one case study, the average home will save 900 to 3000 gallons of water a year for each plumbing fixture.
I invite you to read my full article on the pros and cons of hot water recirculating systems here.
Under sink hot water recirculators are similar to their popular cousins except for the fact that the sensor valve is an built-in component.
Basically, it means that you can install this pump under a bathroom sink without the need for installing a separate sensor valve.
These units also frequently come with timers so you can program them for peak water use in the morning and evening.
If you just hate the thought of messing with your plumbing above the water heater, then this may be the solution for your problem. Instead of just having two plumbing nipples, these under sink recirculators have four threaded plumbing nipples.
Basically, you connect the flex piping coming out of the wall to the cold & hot inlet nipples, and then install two new flexible hoses to the cold & hot outlet nipples — and then connect to under the sink faucet. It’s pretty easy.
However, one downside of under sink recirculators is that if the sensor valve goes bad, you may need to replace the entire pump.
To read my full article on the best under sink hot water recirculation systems, you can read it here.
Hot water recirculating pumps work by using a specialized one way water valve called a sensor valve.
This water valve is installed under the farthest sink away from the water heater. There are also all-in-one under sink pumps where the sensor valve is built into the unit.
When the sensor valve detects that the hot water temperature has gone below around 90 degrees, it will automatically open.
When the valve opens, the recirculating pump detects the pressure change, turns on, and pumps hot water through the hot water line. But where does the standing lukewarm water go?
The recirculator will send this lukewarm water back to the water heater through the cold water supply line. It basically uses the cold water supply line as a temporary return. A few homes will actually have a dedicated hot water return line creating a hot water loop.
Most homeowners will also have timers attached to the recirculating system so that it will only turn on for a few hours in the morning and a few hours in the evening.
If you would like to read more on how hot water recirculating pumps work, you can check out my article here.
Installing hot water recirculating systems can take anywhere from 2-4 hours depending on the complexity of your setup.
The biggest step with recirculator installs is draining the water heater and connecting the pipes to the pump (above the water heater).
If you have threaded flexible piping into your water heater, you can count yourself lucky — because the install will be much easier.
If you have hard copper or CPVC to the water heater, you may want to employ a qualified plumber because these pipes will have to be cut and re-soldered or glued. After the pump is installed above the water heater, the next step is to install the sensor valve at the farthest sink away from the water heater.
The sensor valve will open & close based on the hot water temperature. When the hot water drops to around 95 degrees, the one way sensor valve will open, sending the lukewarm water back to the water heater.
How does it do this feat?
It temporarily uses the cold water supply line as a return back to the water heater — creating a transient hot water loop.
A few homes already have a dedicated hot water loop installed, but these are almost always on new homes. Most recirculator installs will be on homes without these dedicated loops.
Grundfos is a multi-billion dollar company based in Denmark.
It is world-renowned for its design and manufacture of specialized water pumps — for residential and commercial applications.
Grundfos was founded in 1945 and currently employs over 10,000 employees worldwide — some of the highest quality hot water recirculating pumps are made by Grundfos.
My top recommendation for the best Grundfos hot water recirculator probably goes to their 595916 model. This quiet pump comes with a built-in timer that you can easily program to turn on the pump only during peak water use in the morning or evening.
The Grundfos 595916 is highly efficient and it can pump up to 9 gallons per minute. It comes with a 6-ft power cord so you can just plug it into a standard 120-volt outlet.
There is no need for a dedicated hot water loop — it will temporarily use the cold water supply line to send lukewarm water back to the water heater — creating an on demand hot water loop.
To get more info on my top picks for the best hot water recirculating pumps made by Grundfos, you can view it right here.
These tankless units heat up the water instantly as it passes through, and they are used for just a single fixture such as a shower. (Sometimes a few plumbing fixtures.) There is no need for a storage tank so it takes up less space.
In addition to single fixture tankless heaters, there are also electric shower head heaters. These are similar to tankless water heaters in that they heat up the water instantly as it passes through except that it is all in the shower head. Shower head heater will need to be installed by a qualified electrician (for obvious reasons) and will usually need a dedicated circuit at the electrical panel.
There are also mini-tank water heaters which will actually act like a mini water heater — holding and heating water — while being small enough to install under a sink or on a bathroom wall.
Even though I think hot water recirculators are your best bet — why settle for instant hot water to just one shower when you can have it for the whole home — there are other cool products on the market.
What's The Bottom Line?
Some homes just take longer to get hot water at the beginning of the day (or after a long work day).
There are numerous factors that influence hot water speed such as:
- the size of the water pipes (larger pipes take longer)
- square footage of home and number of levels (big homes take longer)
- pipe branching (just one hot water main branch or multiple)
In my opinion, the best way to get instant hot water is with a hot water recirculating pump coupled with a timer.
Look, the energy and cost involved in domestic hot water for homes is second only to the HVAC system — installing a hot water recirculator can save over 10,000 gallons of water a year for the average household.
But the most immediate benefit is the it prevents waiting several minutes for hot water in the early morning. The most common install is above the water heater with a sensor valve installed under the farthest sink.
You can also install under sink recirculators that have the sensor valve as a built-in part of the pump.
In addition to hot water pumps, there are also single-fixture mini tank water heaters and on demand tankless heaters — these are also installed under the sink or next to the fixture.
And lastly, there are the somewhat infamous electric shower head heaters. These shower head heaters are more popular in Asia and Latin America but if installed by a qualified electrician — they can be a safe way to get an instant hot water shower.