Hot Water Recirculation Pump Installation (12 Step Guide)

Do you want to know how to properly install a hot water recirculating pump? 

Instant hot water pumps can be a great feature to any homeowner that is tired of waiting for hot water in the morning.

Here is my full review on the best hot water recirculating pumps.

In this guide, I will go over...

  • How to drain the water heater
  • How to install the recirculation pump above the water heater
  • And how to install the sensor valve under the farthest sink

Let's get started with this guide!

how to install a hot water recirculating pump

A Quick Breakdown On Hot Water Recirculation Pump Installs

In this article, I will give a general overview of what it takes to install most hot water recirculation systems. 

My main reference for this guide is the manufacturer recommendations for installing the Watts 500800 Hot Water Recirculating Pump. If you have any doubts, it is always best to contact a qualified plumber. Some cities & counties may also require obtaining a permit through a licensed plumber.

If your piping above the water heater isn't easily removable flex piping (such as stainless steel braided), and it is copper or CPVC, then having a qualified plumber do the installation is recommended.

The most common type of hot water recirculation pump is installed above the water heater. (There are a few pumps designed to be installed under a sink fixture which have their sensor valve as an in-built part of the pump.)

In addition to the the pump, there is a sensor valve that will need to be installed at the farthest sink away from the water heater.

Most homes don't have dedicated return lines just for the recirculating pump. What I usually see is that the water pump sends the lukewarm water in the hot water line back to the water heater through the cold supply line.

That is where the sensor valve comes in to play. The sensor valve will open when the water temperature in the hot line drops to around 95 degrees. Basically, the circulator temporarily uses the cold water line as a return line.

Read Also: What Are The Best Hot Water Recirculating Pumps? (Review)

#1. Turn Off Water Heater Breaker And Gas Valve

The first step in installing a hot water recirculator is to turn off the power to the water heater.

Locate the breaker at the electrical panel, it will usually be a 30-amp breaker --- flip the switch. In addition to turning off the power to the water heater, you will want to turn off the gas valve to the water heater --- if it's electric you can ignore this step.

There should be a red or yellow gas valve close to the water heater, just follow the gas line that comes out of the water heater. Turn the gas valve in a perpendicular direction to shutoff the gas.

If you have an older water heater, and there is a pilot light, please make sure that the pilot is extinguished.

Read Also: What Are The Pros & Cons of Hot Water Recirculating Pumps?

#2. Shut Off Water To Water Heater

Now you will need to turn off the water.

The easiest way is to close the water valve that is directly above the water heater --- which should be there, or at least close by. Turn this valve to a perpendicular direction.

If you can't find the supply valve or if you have any doubts, you can turn off the main water valve for the entire home.

Read Also: What Are The Best Under Sink Hot Water Recirculation Systems?

#3. Drain Hot Water From Fixtures

After shutting off the water supply, you will need to drain or flush the hot water from all of the home's piping.

All you have to do is locate the lowest fixture in the home, and open the hot water. Let all of the home's hot water drain out. If it doesn't stop draining, then you know you may still have water going to the water heater.

how to install a hot water recirculating pump (check valve operation) (1)

#4. Drain The Water Heater

After draining the hot water from the piping, you will need to drain the water heater.

Water heaters have drain valves (threaded hose spigot) at their bottoms. Connect a hose to the spigot, and open the water valve with a flat head screwdriver. Drain the water to a nearby drain or utility sink.

After draining, close the valve with the flat head screwdriver.

Read Also: How Does A Hot Water Recirculating Pump Work?

#5. Remove Hot Water Pipe From Water Heater

Now that you have drained all of the hot water from the home's piping and water heater, it is time to remove the hot water outlet pipe from the water heater.

Hopefully you have braided flex piping that is easily removable.

With this 3/4" flex pipe connection, all you have to do is use a wrench, loosen the nut, and remove the piping. If you have copper, CPVC, or PEX, and cuts or soldering is required, you may want to hire a competent plumber.

#6. Connect Pump To Threaded Nipple

Once you have removed the hot water discharge piping, you can simply install the water pump onto the hot water outlet threaded nipple.

Make sure that the water pump is installed correctly, with the arrow on the housing pointing in the direction of water flow (away from the water heater). Always remember: If there is a rubber gasket on a female threaded nipple, then teflon plumbing tape is not required.

#7. Connect Hot Water Supply Line To The Pump

Since you just installed the recirculating pump to the water heater, now you need to connect the hot water line to the water pump outlet nipple. Simply tighten the 3/4" nut with a wrench.

If the flex piping female end doesn't have a rubber gasket, then install teflon tape to ensure a leak free connection.

Read Also: What Are The Best Grundfos Hot Water Recirculators?

#8. Turn On Water

It is time to turn back on the water to the water heater (or whole house). 

After the water heater has filled up, run a plumbing fixture until all of the air has been removed from the home's piping.

#9. Locate Sink Farthest From Circulation Pump

Once you have installed the recirculation pump, you will want to locate the sink farthest from the water heater in order to install the sensor valve.

If you have trouble determining the farthest sink, then find the sink that takes the longest for hot water to arrive.

how to install a hot water recirculating pump (sensor valve)

Sensor Valve With 1/2" Threaded Nipples

#10. Shut Off Sink Water (Stop) Valves

Now it's time to shutoff the water to the sink. There will be one shutoff valve for hot water and one for cold water. Turn the stop valves under the sink perpendicular or pull out it is a push/pull type with a circular handle.

Read Also: How To Get An Instant Hot Water Shower? (All Products)

#11. Remove & Connect Flex Lines To Sensor Valve

Remove the flex water lines directly from the stop valves near the wall (not the ends under the sink).

These flex water line ends will either be 1/2" or 3/8". If your sink supply lines are solid metal such as copper or steel, you will want to replace these with flexible stainless steel braided type.

The sensor valve will likely only have 1/2" connections.

You can buy flex pipes with 1/2" to 3/8" ends --- 1/2" to 1/2" ends --- or 3/8" to 3/8". You can also buy 1/2" to 3/8" adapter fittings instead of buying new hoses.

Basically, you connect the supply water lines to the cold & hot water outlets on the top of the sensor valve. And then you connect new flex lines from the stop valves to the sides of the sensor valve.

sensor valve (hot water recirculating pump) (1)

#12. Install More Than One Sensor Valve

If you have a very large house and have branched piping, where there is more than one hot water main, you may want to install another sensor valve at a different location of the house.

In addition, you can also install sensor valves in parallel under the same sink in order to increase the water flow and to reduce lower temperatures.

Read Also: What Are The Best Dual Flush Toilets? (Review)

how to install a hot water recirculating pump (parallel sensor valves)

Final Thoughts On Installing Hot Water Recirculation Systems

Frankly, if you already have flex lines connected to the top of your water heater, the installation of a recirculation pump and sensor valve shouldn't take too long.

However, if you have to solder together piping, or glue together sections of CPVC, it can become a significantly more difficult job for the average homeowner.

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5 thoughts on “Hot Water Recirculation Pump Installation (12 Step Guide)”

  1. You mentioned the ‘parallel sensor valve’ installation at one sink that is also mentioned in the Watts 500800 manual.

    I am considering doing this, but I am a bit wary because I cannot find ANY examples of it from google searches or youtube.

    Have you seen the parallel sensor valve installation in an actual installation?
    I get what the parallel install is doing. I am just nervous about it due to finding so little info/examples of it.
    (It’s pretty rare when you fined NOONE on Youtube making a video about DIY home stuff!)


  2. Looks like all your comments refer to regular water heaters. I have a Rheem tankless water heater Model #RTGH 95DVN. What is the best way to install a recirculation system? At the heater or under the sink? What brand do you recommend for which ever is appropriate?

    • Hello Jim,

      Standard above the water heater recirculating pumps or “comfort systems” do not typically work with tankless water heaters because the sensor valve doesn’t produce enough water flow to trigger the tankless water heater.

      Most under sink recirculators will work with tankless water heaters however. PROZRTED is a nice unit you may want to check out.


  3. When the recirculating pump under the sink and furthest away from the hot water heater is on I get hot water out of both the hot and cold water spickets. Is that normal.


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