What are Hot Water Recirculating Pumps?

Having hot water on demand is a convenience that many of us take for granted. Imagine taking a shower on a cold winter morning, and you can instantly appreciate this luxury we have on tap, pun intended.

But showers are one thing. Imagine cooking in the kitchen, and getting some egg or other foodstuff on your hand. You just need a quick 5-second spurt of hot water to wash off the gunk. Instead, you stand there for nearly half a minute with egg yolk on your hand, waiting for the water to heat up. Meanwhile, gallons of cool but perfectly clean water run down the drain.

Hot water recirculation pumps are one way to shorten the waiting time, while reducing unnecessary water wastage.

What are Hot Water Recirculating Pumps?

Also called hot water recirculation pumps or simply circulating pumps, these dedicated pumps are connected to the water heater and return unused hot water back to the heater. Their purpose is twofold:

  • Reduce the time it takes for water to heat up
  • Cut down on cold water wastage

Recirculation pumps work by using temperature sensors to monitor the water temperature, while a check valve stops water from going back to the return plumbing line. This way, it returns water in the line back to the water heater, reducing the time it takes to reach the faucet.

What are the Different Types of Hot Water Recirculation Pumps?

Hot water recirculation pumps come in two versions, each with their own pros and cons:

Full recirculating pump system

These use a dedicated hot water return pipe connected to the plumbing system. It creates a loop from the water heater to the different fixtures, and back again. Any unused hot water gets shunted into this loop by the pump, so that hot water is always instantly available instead of being left in the main pipe to get cold.

To reduce heating costs, most full recirculating pumps use sensors to shut off the flow when the hot water has made a complete loop. Some also incorporate timers that allow users to schedule the pump’s operation and shut it off during low-demand hours, such as at night or during working hours.

Unlike the full recirculating pump, this one uses the existing cold water line to return the unused hot water back to the heater. 

Since it doesn’t require a dedicated hot water line, this is a more budget-friendly option. However, since the hot and cold water share the same pipe, cold water can sometimes come out lukewarm or take time to get cold. This can be a particular concern for homes equipped with an evaporative cooler.

 

Hot Water Recirculating Pump Comparison

Criteria

Full Recirculating Pump

Recirculating Pump Comfort System

Design

Requires an additional pipe Uses existing cold water pipe

Pros

Faster hot water delivery Lower initial cost

Cons

  • Higher upfront cost
  • Can be difficult to install in some residential designs
  • Can cause cold water to be lukewarm
  • Cold water takes time to cool

Best used for

  • New homes under construction
  • Homes under extensive remodeling / replumbing
  • New home additions that require new plumbing to be installed
  • Hard-to-access plumbing lines
  • Residential designs where new line installation can be a challenge
  • Smaller budgets

 

What are the Benefits of a Hot Water Recirculation System?

Convenience

A recirculation system considerably reduces the time it takes for water to heat up, providing users with instant hot water on tap.

 

Increased water savings

According to the EPA, the average American home wastes more than 3,650 gallons of water per year waiting for hot water to arrive at the point of use. A recirculation system cuts down on water losses by delivering nearly instant hot water for use instead of wasting water while waiting for it to heat up.

 

Lower utility costs

Based on the Energy Information Administration’s Office of Energy Consumption and Efficiency Statistics, heating water is the second largest use of energy in an average home (after space heating and cooling). A recirculation pump can lower the cost by reducing the amount of hot water needed.

 

Smart heating

Some pumps are equipped with timers, or can be programmed to operate only in periods when hot water demand is high (for example, they can automatically turn on during the morning and shut off during working hours). This cuts down on unneeded heating, and reduces costs and wear.

 

Rebates

Some jurisdictions where water is scarce provide rebates on the purchase and  installation costs of recirculating systems. For example, some cities in New Mexico provide a $100 rebate, while it can go up to $200 for some cities in Arizona.

 

What are the Drawbacks of a Hot Water Recirculation System?

X Requires a power source near the installation site

  • This can limit installation locations, or need rewiring.
  • It can be dangerous if the pump suffers a leak.

X Model limitations

  • Full recirculating systems: can be pricey and require extensive installation.
  • Comfort systems: can result in lukewarm water, especially in warmer climates or during the hot season .
  • Pumps with scheduled timers will not provide hot water on off-demand hours. This can be jarring for homeowners who require hot water at inconvenient times.

X Cold climate limitations

  • Pumps located in colder areas or during the cold season can produce low output.

X Requires good plumbing systems

  • Old or poorly insulated pipes can result in higher heat loss.
  • This can strain the pump by forcing it to run longer, and also result in higher energy costs.

X Rebate requirements

  • To qualify for a rebate, some cities and municipalities set efficiency standards on the pump. Some require UL certification while others look at the installation.

 

What to Look For in a Recirculating Pump

Recirculating pumps come in a wide variety of types and designs to accommodate different water heaters. Some of the things you should look for are:

☑ Water heater compatibility

Before looking at recirculating pumps, note what type of hot water heater you have. Tankless water heaters generally require higher power pumps, and should be taken into account. Most pumps may not have the necessary power to be compatible with upscale gas or electric tankless water heaters.

☑ Housing material

Cast iron may be more durable and longer lasting than aluminum. However, it is not recommended for potable water use since rust can develop in the system. Premium pumps use stainless steel, which combines the durability and longevity of cast iron with the rust-proof quality of aluminum. 

☑ Timer

This is a useful feature to have if your household has a peak hot water usage time, so you can limit the power needed for heating water only to peak hours. Timers are also recommended in states where electrical costs come at a premium.

☑ Manual vs automatic activation

Some pumps have manual on/off buttons: these need to be switched on before using the faucet. These pumps are ideal for smaller homes where hot water demand is limited to a few fixtures, such a single bathroom.

Other systems use temperature sensors that automatically activate the pump if the water in the line falls below a preset value. These are recommended for larger homes with more water fixtures or higher hot water demand.

 

Choosing the Right Hot Water Recirculating Pump for your Home

To make your selection easier, here’s a handy chart of the hot water recirculation systems we carry and their ideal use cases.

Plumbing Setup Water Heater Setup Installation Requirements Recommended Model
For homes WITH a dedicated return line
Hot water storage tank
AMH2K-7
Tankless water heater AMH2K-R
For homes WITHOUT a dedicated return line
Hot water storage tank
There is space or power under the sink AMH3K-7
No space or power under the sink AMH1K-3UV
Tankless water heater
There is space or power under the sink AMH3K-R
No space or power under the sink AMH1K-6ODRZT1
No space or power under the sink, and you prefer on-demand hot water AMH1K-RODRN

 

The Best Hot Water Recirculating Pumps for 2021

Here is our top selection of hot water recirculation pumps for each category:

Best Budget Under Sink Hot Water Recirculation Pump:

AquaMotion AMH3K-7 Under Sink Hot Water Recirculation Pump Kit with Timer

AquaMotion AMH3K-7 Under Sink Hot Water Recirculation Pump Kit with Timer

Price: $315

The AMH3K-7 is designed for single pipe hot water tanks with no return line. As an under sink model, it is compact enough for most under sink spaces and installs quickly without any pipe cutting required: simply attach to the water hoses at the valve and plug in.

The pump features a 24-hour mechanical timer with 15-minute increment tabs and built-in, non-adjustable Aquastat. The Aquastat will tell the pump to run when it senses the water at the fixture is starting to drop below 85°F and will run for about a minute or so until it reaches 105°F degrees and shuts off. The pump will run about 3 times per hour for less than 5 minutes.

In addition, all of the moving parts are housed in a “Green Eco Cartridge Design”. It is the only field serviceable and replaceable cartridge available, making maintenance and replacement quick and easy.

 

Best Hot Water Recirculation Pump for 3 Pipe Hot Water Heaters:


AquaMotion AMH2K-R 3 Speed Hot Water Recirculation Pump

Price: $425

The AquaMotion AMH2K-R is designed for hot water heaters with a dedicated return line. It installs right into the return line near the tankless heater, and does not require power or room under any sink.

This 3-speed circulator comes with a built-in mechanical timer and Aquastat. The 3 speeds allow it to be used with either a storage tank or tankless hot water heaters. The pump is rated for up to 125 PSI water pressure, with a maximum ambient water temperature of 104°F.

 

Best Hot Water Recirculation Pump for Tankless Water Heaters:

AquaMotion AMH1K-RODRN On-Demand Hot Water Recirculation Pump
AquaMotion AMH1K-RODRN On-Demand Hot Water Recirculation Pump

Price: $599

This pump is designed for use with single pipe, tankless hot water heaters without a built-in pump or dedicated return line. As an on-demand model, it does not come with a timer, but includes AquaMotion’s AMK-WB On-Demand Wireless Control Kit. The AMR-SFVL1 high speed circulator provides single speed with check valve and line cord. 

Also included is an AquaMotion ODR valve (for under sink installation). The ODR installs at the fixture furthest from the tankless hot water heater and acts in conjunction with a circulator to supply hot water on demand or with a built-in timer on the pump.

 

You can also view our complete selection of hot water recirculation pump kits from AquaMotion and Rinnai, catering to different water heaters, price points, and needs.

Mickey Luongo

Mickey is the resident heating and air conditioning expert with over 15 years of experience in the industry.

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