Navien Constantly Running: Recirculation or a Leak?
On this page (6 sections)
The Short Answer: Most Navien heaters that “never stop” are recirculating. On NPE-A2 models, the built-in pump circulates water and the burner fires briefly to keep the loop hot, even with no tap open. Turn recirculation off and close every tap. If the burner still fires, hot water is flowing somewhere: a dripping fixture, a leak, or a crossover. If it fires with the supply closed, call for service.
Is it the pump or the burner?
The front panel shows whether the burner is firing (flame icon) and, on A2 models, whether recirculation is active. Listen too: a pump makes a quiet hum, while the combustion fan makes a louder whoosh.
| What’s happening | Meaning |
|---|---|
| Pump running, burner off most of the time, firing briefly now and then | Normal recirculation keeping the loop warm |
| Burner firing in short bursts all day with recirculation on | Recirculation set to run all the time, or a long, uninsulated loop losing heat |
| Burner firing with recirculation off and no taps open | Hot water is flowing somewhere: a leak, drip, or crossover |
| Burner firing with the heater’s cold supply valve closed | Control or flow sensor problem; needs service |
| Combi unit firing with no hot water use | Probably heating the house, which is normal for a combi |
Recirculation settings
Navien A2 models can recirculate internally through a small buffer tank, or externally through a return line from the farthest fixture. Depending on model and accessories, recirculation can run continuously, on a schedule, in an adaptive mode, or on demand with a button. Continuous mode keeps the burner cycling all day to replace heat lost from the pipes. That’s often what owners hear.
Changing to a schedule that covers your morning and evening use, or to on-demand control, usually cuts the running time a lot. If your installer set up external recirculation, make sure the mode on the panel matches the plumbing. A heater set for external recirculation with no return line in place won’t behave as expected. For waiting times, see Navien hot water takes too long.
When hot water is really flowing
Navien’s manual gives 0.5 gallons per minute as the draw needed for hot water. A slow drip won’t reach that, but a faucet left slightly open, a single-handle faucet or shower valve with a worn cartridge, a fixture that doesn’t shut off fully, or a hidden leak in hot piping in a wall or slab can push flow over the threshold, often in bursts.
A failed check valve or mixing valve can also let water flow through the heater when no tap is open, by circulating from the hot side to the cold side.
What you can check safely
- Turn recirculation off from the front panel or app, and close every tap.
- Watch the flame icon for several minutes. If it stays off, recirculation was the cause.
- If it still fires, walk the house: check that every faucet and shower is fully off, look under sinks, and listen for running water. Check your water meter. If the leak indicator turns with everything off, water is leaking somewhere.
- Feel the cold pipes near fixtures. A cold line that is warm suggests a crossover.
- Close the cold water supply valve at the heater. If the burner still fires, stop and arrange service.
What the technician will check
A plumber will check the recirculation configuration and schedule, test check valves on the return line and at crossover valves, and look for crossovers at mixing valves. If the heater fires without flow, a technician checks the flow sensor and control. Navien lists E439 as a flow sensor fault on NPE-2 models. A leak detection specialist may be needed for hidden leaks in walls or slabs.
Frequently Asked Questions
Q: Does continuous recirculation damage the heater? A: It doesn’t damage it, but it adds burner cycles and pump hours, and it uses more gas and electricity. Scheduled or on-demand recirculation is gentler and cheaper to run.
Q: My Navien fires every few minutes at night. Is that a leak? A: Check whether recirculation is scheduled overnight. If it isn’t, and the heater still fires with all taps off, look for a hot-water leak or crossover.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Navien NPE-2 Series user's information manual (opens in a new tab)Navien NPE-A2 and NPE-S2: recirculation modes, built-in pump on A2, 0.5 GPM minimum flow.
- Navien: manuals and product documents (opens in a new tab)Model-specific owner information; service manuals are intended for qualified professionals.
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