A hot water recirculation pump keeps hot water close to your fixtures by moving the cooled water in the hot pipes back to the water heater, so a tap runs hot in seconds instead of a minute. Systems use either a dedicated return pipe or a crossover valve that sends water back through the cold line. On-demand controls save the most energy; always-on loops can waste a lot.
- The wait for hot water is the time to empty the pipe between heater and tap: roughly 0.15 L per metre of 1/2-inch copper and 0.31 L per metre of 3/4-inch.
- Dedicated return loops work best; crossover (comfort) valve kits need no new pipe but warm the cold line at the far fixture.
- On-demand pumps triggered by a button or sensor use far less energy than pumps running around the clock.
- A recirculation loop adds heat loss to the pipes, which ratings like UEF do not include; insulate the loop.
- With tankless heaters, check the model supports recirculation; some have built-in pumps and settings for it.
01 /Why does hot water take so long to reach the tap?
Hot water takes time because the pipe between the water heater and the tap is full of water that has cooled since the last use, and all of it has to run out before hot water arrives. Tankless heaters do not change this; the pipe still has to empty.
The volume adds up quickly. A metre of 1/2-inch copper holds about 0.15 litres, 3/4-inch copper about 0.31 litres, and 1/2-inch PEX about 0.11 litres. A far bathroom fed by 10 metres of 3/4-inch trunk and 5 metres of 1/2-inch branch holds nearly 4 litres of cooled water. At a lavatory faucet running about 5.7 L/min, that is roughly 40 seconds of cold water down the drain before it warms, and more once the pipe itself has soaked up some heat.
| Pipe | Litres per metre | Litres in 15 m |
|---|---|---|
| 1/2-inch PEX | 0.11 | 1.7 |
| 1/2-inch copper | 0.15 | 2.3 |
| 3/4-inch PEX | 0.24 | 3.5 |
| 3/4-inch copper | 0.31 | 4.7 |
Natural Resources Canada's Water Heater Guide points to the cheapest fix of all when you are replacing a heater: if venting allows, locate the heater closer to the most-used fixtures to shorten pipes, which saves energy and water. When that is not possible, recirculation is the usual answer.
02 /What types of hot water recirculation systems are there?
There are two ways to get the water back to the heater, and several ways to decide when the pump runs.
| Control | How it decides to run | Energy use |
|---|---|---|
| Continuous | Runs all the time | Highest; the loop is hot 24 hours a day |
| Timer | Runs during set morning and evening windows | Moderate; wasted outside actual use |
| Thermostatic (aquastat) | Runs until the return water reaches a set temperature, then stops | Moderate; keeps the loop warm all day |
| On-demand (button, motion sensor or smart trigger) | Runs only when someone is about to use hot water, then stops when the loop is hot | Lowest |
03 /Do recirculation pumps waste energy?
They can. A recirculation loop turns your hot water pipes into a radiator: any time the loop is kept hot, it loses heat through the pipe walls, and the water heater replaces that heat. The pump motor also uses a little electricity. None of that is captured in the heater's uniform energy factor, which covers the heater alone; see the efficiency and UEF guide.
The saving is in water and time. The waste depends on how long the loop stays hot. A continuously running, uninsulated loop can add a meaningful share to a household's water heating energy; an insulated loop on an on-demand control adds very little, because it runs only for the minute before someone uses hot water. Practical rules:
- Prefer on-demand controls. If you use a timer, keep the windows tight to real routines.
- Insulate the whole loop, including the return. Natural Resources Canada calls insulating hot and cold pipes near the heater the most cost-effective improvement for any installation.
- Keep the loop short and the pump small; a residential loop needs very little flow.
- On a heat pump water heater, returning warm water to the tank disturbs stratification and can reduce efficiency; follow the manufacturer's guidance on where and how to connect a return.
To see what your household's hot water costs before adding loop losses, run your numbers through the Energy Cost Comparer.
04 /How do recirculation pumps work with tankless and mixing valves?
With a tankless heater, recirculation has two jobs: keep the pipe warm and avoid the cold slug and minimum-flow problems described in the tankless vs tank guide. Some tankless models include an internal pump and recirculation settings; others permit an external pump only in specific configurations. Continuous recirculation through a tankless unit makes it fire often, adding wear, so on-demand control is especially valuable here.
With a thermostatic mixing valve at the heater, the return line has to be piped so that recirculated water does not upset the mixing valve's blend or bypass it. Mixing valve manufacturers publish specific piping diagrams for recirculating systems. If you store at 60 °C and mix down, as public health guidance suggests, make sure the design is done by someone familiar with these diagrams.
05 /Are there alternatives to a recirculation pump?
Yes, and at replacement or renovation time they are often cheaper to run than a loop. The goal is the same in every case: reduce the volume of cooled water standing between the heat source and the tap.
| Approach | How it helps | Best time to do it |
|---|---|---|
| Move the water heater closer to the main bathrooms | Shorter trunk line, less water to purge, lower pipe losses | When switching to sidewall venting, electric or heat pump |
| Smaller-diameter branch lines | A 1/2-inch line holds about half the water of a 3/4-inch line per metre | Renovations with open walls |
| Manifold (home-run) PEX to each fixture | Each fixture gets its own small line, so only that line has to purge | New builds and gut renovations |
| Point-of-use electric heater at a far sink | Heats water right at the fixture | One remote fixture with a spare circuit |
| Insulating existing hot lines | Water in the pipe stays warm longer between uses | Any time the pipes are reachable |
These options also avoid the loop losses that come with recirculation, so they are worth pricing alongside a pump when walls are open or the heater is being relocated anyway.
06 /What should a recirculation installation include?
- Choose the loop type
A dedicated return where you can run pipe; a crossover valve kit where walls and ceilings are finished.
- Use a pump rated for potable water
Bronze or stainless steel pump bodies suit domestic hot water; cast iron heating circulators do not.
- Add check and isolation valves
A check valve prevents backward flow; isolation valves let the pump be serviced without draining the system.
- Power and control
An outlet near the pump and the control you have chosen: button, motion sensor, timer or aquastat.
- Insulate
Insulate the supply and return pipes along their full accessible length.
- Balance and test
Confirm the far fixture warms quickly and the pump shuts off when the loop is hot.
| Option | Typical range, installed |
|---|---|
| Crossover valve kit with pump at the heater, existing home | $500–$1,200 |
| On-demand pump with dedicated return, piping accessible | $900–$2,500 |
| New dedicated return line through finished walls | $2,000–$5,000+ |
If you are replacing your water heater, adding recirculation at the same time saves a visit. Mention it in your quote request.
FAQQuestions people ask
Do hot water recirculation pumps save water?
Yes. They save the cold water that would otherwise run down the drain while you wait for hot water, which can be several litres per use at a distant fixture.
Will a recirculation pump raise my energy bill?
It can, mainly through heat lost from the loop. On-demand controls and pipe insulation keep the increase small; an uninsulated loop running all day can add noticeably.
Can I add a recirculation pump without a return line?
Yes, with a crossover or comfort valve kit that sends water back through the cold line from under the farthest sink. The trade-off is lukewarm water from that sink's cold tap at first.
Do recirculation pumps work with tankless water heaters?
Many do, and some tankless units have built-in pumps. Check the model's instructions, and prefer on-demand control to limit burner cycling.
Is a recirculation pump the same as a point-of-use heater?
No. A point-of-use heater is a small electric heater at the fixture that heats water there. It avoids long waits at one tap without a loop, but adds an electrical load and another appliance.