To reset a tankless water heater, first turn off the unit using its power switch or circuit breaker, wait 60 seconds, then turn it back on. This simple power cycle clears most temporary error codes and restores normal operation. If your tankless water heater has stopped producing hot water or is flashing an error code, a reset is often the first fix to try. Below we walk through the complete process, common error codes, and when to call a professional.
Why Your Tankless Water Heater Might Need a Reset
Tankless water heaters use advanced electronics and sensors to heat water on demand. A reset is typically needed when the unit’s internal computer detects an anomaly — such as a gas supply interruption, a blocked vent, or a sudden voltage fluctuation. According to the U.S. Department of Energy’s water heating guide, modern tankless units have built-in self-diagnostics that trigger error codes and shut down the heater to prevent damage. Resetting clears the error memory and lets the unit restart safely.
Before You Start: Safety First
- Turn off the gas supply valve (for gas models) or the electrical disconnect (for electric models).
- Wait at least 5 minutes to allow any residual gas to dissipate if you smell gas — then call a professional.
- Keep the area around the unit clear of flammable materials.
- If you see any water pooling near the unit, turn off the water supply and contact water heater repair before proceeding.
How to Reset a Tankless Water Heater – 5 Steps
Step 1: Locate the Power Source
Find the unit’s power switch (usually on the side of the case) or the dedicated circuit breaker in your electrical panel. For gas models, also locate the gas shut-off valve.
Step 2: Turn Off the Unit
Flip the power switch to OFF, or turn off the circuit breaker. For gas units, close the gas valve. Wait at least 60 seconds (some manufacturers recommend 5 minutes for full discharge).
Step 3: Restore Power
Turn the power switch back ON or flip the breaker to ON. For gas models, slowly reopen the gas valve. Listen for the ignition sequence — you should hear a clicking sound and then the burner ignite.
Step 4: Check the Display Panel
Most tankless units have a digital display. After resetting, the display should show normal operating status (often the current water temperature). If an error code reappears, note the code and consult the manual.
Step 5: Run Hot Water
Open a hot water faucet and let it run for 30–60 seconds. The unit should fire up and deliver hot water. If not, repeat the reset or proceed to troubleshooting.
Common Error Codes and What They Mean
| Error Code | Meaning | What to Do |
|---|---|---|
| 11 | No ignition (gas model) | Check gas supply; reset; if persists, call a plumber. |
| 12 | Flame failure | Clean the burner and vent; reset once. |
| 14 | Overheat | Turn off unit, wait 30 minutes, reset. Check for blocked vent. |
| 16 | Outdoor unit frozen | Thaw unit with warm air; do not use open flame. |
| 29 | Gas supply pressure abnormal | Contact your gas utility or a licensed plumber. |
| 99 | Internal communication error | Power cycle unit; if code returns, professional service needed. |
Note: Error codes vary by brand. Always refer to your owner’s manual. For persistent issues, schedule water heater repair.
When a Reset Doesn’t Work – Troubleshooting Tips
Check the Water Supply
A partially closed water shut-off valve or a clogged inlet filter can prevent the heater from operating. Turn off the unit, close the water valves, remove the inlet filter, and rinse it clean. The Environmental Protection Agency’s WaterSense program notes that sediment buildup reduces efficiency — flushing the unit annually helps.
Inspect the Venting System
Blocked vents can cause the unit to shut down as a safety measure. Check for debris, bird nests, or snow buildup around the exhaust vent. Clear any obstructions and reset the unit.
Verify Gas Supply (Gas Models)
Ensure the gas valve is fully open and that other gas appliances in your home are working. If they aren’t, the issue may be with your gas line — call your utility company. For help with gas line issues, contact pipe repair services.
When to Call a Professional Plumber
If your tankless water heater still won’t reset after following these steps, or if you see error codes like 12, 14, or 99 repeatedly, it’s time to call a licensed plumber. Internal component failures — such as a bad circuit board, a failed gas valve, or a blocked heat exchanger — require professional diagnosis and tools. Attempting advanced repairs without training can void the warranty and create safety hazards. The International Association of Plumbing and Mechanical Officials (IAPMO) recommends annual professional maintenance for tankless units (IAPMO).
Preventive Maintenance to Avoid Future Resets
- Flush the unit annually with a descaling solution to remove mineral buildup (especially in hard water areas).
- Clean the inlet filter every 3–6 months.
- Inspect the vent and intake for blockages before each heating season.
- Test the pressure relief valve yearly.
- Consider installing a water softener to reduce scale accumulation.
Frequently Asked Questions
1. How often should I reset my tankless water heater?
Only reset when the unit displays an error code or stops heating water. Frequent resets may indicate an underlying issue that needs professional attention.
2. Will resetting my tankless water heater erase the error code memory?
Yes, a power cycle clears temporary error codes. However, if the root cause remains, the error will return.
3. Can I reset a tankless water heater from the remote control?
Some models allow a remote reset, but the most reliable method is a full power cycle at the unit or breaker.
4. Is it safe to reset a tankless water heater multiple times?
Resetting once or twice is safe, but repeated resets without fixing the cause can damage the unit. Call a plumber if the problem persists.
5. What should I do if the reset button is broken?
If the physical reset button is stuck or broken, use the circuit breaker to power cycle the unit. Then schedule a repair.
6. Does resetting fix low water pressure?
No. Low water pressure is usually a plumbing issue — check for leaks or clogs. Contact leak detection services if you suspect a hidden leak.
If your tankless water heater continues to give you trouble after trying these steps, don’t hesitate to call the experts. Contact MyTownPlumber today for fast, reliable service — we’ll diagnose the problem and get your hot water back.
— MyTownPlumber Editorial Team