11
Rheem Water Heater
Severity: ModerateWhat it means
Error 11 means the burner did not ignite within the allowed attempts.
The most common causes are no gas supply, a closed shutoff valve, a dirty igniter, or a blocked vent.
Affected Models
- Rheem Performance Tankless
- Rheem Performance Plus Tankless
- Rheem Prestige Tankless
- Rheem Gas Water Heater
- Rheem Marathon
Common Causes
- Gas supply turned off or low pressure
- Dirty or failed igniter
- Blocked exhaust vent or air intake
- Faulty flame sensor unable to detect ignition
- Empty propane tank (LP units)
How to Fix It
-
Verify the gas supply.
Confirm the gas shutoff valve to the water heater is fully open.
Check other gas appliances (stove, dryer) — if they have no gas either, the problem is at the meter or supply line, not the water heater. -
Check the venting and air intake.
Inspect the exhaust vent and air intake openings outside.
Clear any debris, snow, ice, bird nests, or insect screens blocked with lint.
A blocked vent prevents combustion air flow and triggers Error 11. -
Check propane tank level (LP units).
If the unit runs on propane, verify the tank is not empty.
A nearly empty tank can supply low pressure that causes intermittent Error 11.
Refill if low. -
Reset the unit.
Turn off power at the breaker for 30 seconds, then back on.
If Error 11 persists, the igniter, flame sensor, or gas valve has likely failed and requires professional service.
When to Call a Professional
Working with gas appliances carries risk.
If basic checks (gas valve open, vent clear) do not resolve Error 11, contact a licensed plumber or gas technician — do not attempt internal gas component repairs yourself.
Frequently Asked Questions
Is Rheem Error 11 dangerous?
The unit has shut down safely as designed — there is no immediate danger. However, do not bypass the error or repeatedly try to ignite without resolving the cause; trapped gas in a vent system creates a fire and CO risk.
Why does Rheem Error 11 keep coming back after I reset the unit?
A repeating Error 11 means the underlying cause has not been resolved. The most common persistent causes are a faulty igniter, blocked vent, or low gas pressure. A licensed technician can test components.