This small pump is what saves a homeowner from running the tap for a minute or more waiting for hot water to reach a far bathroom.
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Quick answer
A hot water recirculation pump continuously or periodically moves hot water from the water heater through a dedicated return line back to the water heater, keeping the hot water line pre-warmed so fixtures far from the appliance deliver hot water quickly instead of after a long wait. It fails mainly through worn bearings or a seized impeller after years of near-constant running, or through a failed timer or aquastat control that leaves it running when it should not, wasting energy. A recirculation system that suddenly stops delivering fast hot water, or one running around the clock unnecessarily, usually points to this pump or its controls.
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In a home where a bathroom or laundry room sits far from the water heater, hot water can take a long time to travel that distance through the pipe, wasting both time and water while the cooled water already in the line is run down the drain. A recirculation pump solves this by continuously or periodically circulating hot water through a dedicated loop, often using the cold water line as a return path with a check valve, so hot water is already present near the fixture when the tap is opened.
Most residential systems pair the pump with either a timer, so it only runs during hours of expected use, or an aquastat, which senses when the return water has cooled enough to warrant another circulation cycle, both aimed at balancing convenience against unnecessary energy use.
Because these pumps often run for extended periods daily, their bearings and impeller wear faster than most other components in the hot water system. A failing pump typically produces a growing hum, grinding noise, or vibration before it eventually seizes and stops moving water altogether.
Separately, the timer or aquastat controlling when the pump runs can fail in a way that is less obvious: a stuck timer or a miscalibrated aquastat can leave the pump running continuously, which does not necessarily stop hot water delivery but does add unnecessary standby heat loss and gas use over time.
| Symptom | Likely cause |
|---|---|
| Growing hum, grinding, or vibration from the pump | Worn bearings, often a precursor to full seizure |
| Distant fixtures suddenly take as long as before for hot water | Pump has seized or lost power |
| Pump runs constantly at all hours | Failed or miscalibrated timer or aquastat |
| Noticeable increase in gas use with no other explanation | Recirculation running more than intended, adding standby heat loss |
A technician listens to the pump during operation, checks the timer or aquastat's actual schedule against its setting, and verifies the check valve in the return line is holding properly, since a failed check valve can cause hot water to circulate in the wrong direction or bypass the loop entirely. A pump with worn bearings or a seized impeller is replaced outright, while a faulty control is either recalibrated or replaced depending on the fault.
Because a recirculation pump adds continuous demand on the water heater, a technician assessing one also checks how it may be affecting the water heater's own service life, particularly on a tank-style unit where recirculation can accelerate sediment movement.
Safety note
A recirculation pump is typically installed on a natural gas water heater's plumbing, and any work that requires draining or opening that piping should be done by a licensed technician. If you ever smell gas near the water heater, leave the home immediately and call FortisBC at 1-800-663-9911 before doing anything else.
This often means the recirculation pump has seized or lost power, so the loop is no longer keeping hot water pre-warmed near that fixture.
It depends on the control setup; a timer-based system should follow a set schedule, while an aquastat-based system cycles based on temperature, so constant running usually points to a control fault.
It can, since keeping water pre-warmed adds standby heat loss, though a properly scheduled system balances this against the water and time saved at the tap.
Once bearings wear or the impeller seizes, replacement is the typical recommendation rather than attempting an internal repair.
It ensures water only flows in the intended direction through the return loop; a failed check valve can undermine the whole recirculation system even if the pump itself is fine.
This depends heavily on how much the pump runs and the specific model, and a technician can assess wear during a routine service visit.
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