Tankless Water Heater Clicking Noise
On this page (6 sections)
The Short Answer: A few clicks when you open a hot tap, followed by the burner lighting, is the normal sound of a gas tankless heater’s igniter and valves. Clicking that continues without the burner lighting, then an error code, means failed ignition. On electric tankless units, clicks are relays switching heating elements. Clicking when no water is in use usually means something is drawing a small flow.
Normal and abnormal clicks
| What you hear | Heater type | Normal? |
|---|---|---|
| A few rapid clicks, then a soft whoosh and hot water | Gas | Yes, igniter and gas valve |
| One or two clicks when the burner shuts off | Gas | Yes, gas valve closing |
| Rapid clicking that continues, no flame, then a code | Gas | No, ignition failure |
| Clicks, flame lights briefly, goes out, repeats | Gas | No, flame sensing or gas supply |
| A clack as hot water starts and stops | Electric | Usually yes, relays switching |
| Repeated clicking on and off during one shower | Electric | Often flow near the switch-on limit |
| Clicks with no hot water in use | Either | Recirculation, freeze protection, or a small leak |
Gas tankless: clicking without ignition
Gas tankless heaters use an electronic igniter. When it clicks but the burner does not light, the heater is either not getting gas or not detecting flame. After a few attempts, it stops and shows an ignition or flame-failure code; brand pages such as Rheem code 11 and Takagi code 111 explain those.
What you can check:
- The gas valve to the heater is open, and other gas appliances work.
- A propane tank has fuel; regulators can freeze in cold weather.
- The outdoor vent or intake is clear of snow, leaves, or nests.
- Photograph the error code, then reset the heater once by the manual’s method.
If ignition fails again, stop. Repeated attempts send unburned gas into the burner, which can lead to delayed ignition.
What the technician will check: gas pressure, the igniter and its gap, the flame sensor, the gas valve, and the combustion fan. A new installation with an undersized gas line is a common cause when ignition fails only at high demand.
Electric tankless: relays and flow
Whole-house electric tankless heaters switch large currents through relays, which click as they turn heating elements on and off. Clicking that repeats on and off during a single draw often means the flow is hovering around the minimum the heater needs, so it keeps switching. A low-flow head or a mixing valve set mostly to cold can cause this. If clicking comes with a breaker trip, see tankless water heater keeps tripping the breaker.
Clicking when no one is using water
A heater that clicks and fires with all taps closed is seeing flow somewhere. Common sources:
- Recirculation. Built-in or add-on recirculation pumps run on a timer or schedule. Turn recirculation off for a day to test.
- A small leak such as a running toilet, a dripping faucet, or a leak in the plumbing.
- Freeze protection. Outdoor units have electric freeze-protection heaters that switch on in cold weather; you may hear relays even with no flow.
Related guides
Other sounds are covered in tankless water heater banging noise and water heater ticking like a clock. For a tank heater whose igniter clicks without lighting, see water heater burner not lighting.
Frequently Asked Questions
Q: How many clicks are normal before it lights? A: Usually just a few, over a second or two. If the clicking runs much longer than it used to before lighting, have the igniter and gas supply checked.
Q: Can a dirty inlet filter cause clicking? A: Indirectly. A clogged filter can reduce flow enough that the heater keeps starting and stopping, which you may hear as repeated clicking. Clean or have the filter cleaned per your manual.
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.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
- Bosch: electric water heater troubleshooting FAQ (opens in a new tab)Flow and heating-capacity behavior of the Bosch models listed there. Other models use their own limits.
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