Rinnai Tankless Water Heater Code 11 — Ignition Fail Fix

What Does This Error Mean?

Code 11 means the heater tried to ignite and failed.
The igniter clicked, gas was called for, but no flame appeared (or the sensor didn't see one).
Most often it's a closed gas valve or low gas pressure to the unit.
Check the gas valve at the heater is fully on, then test another gas appliance to confirm the supply.
If both are fine and Code 11 persists, call a licensed installer.

Affected Models

Rinnai RU series
Rinnai V series
Rinnai R75LSi
Rinnai RU199iN
Rinnai RUR series

Common Causes

Gas shutoff valve at the heater partly closed
Gas supply low or interrupted to the house
Air in the gas line after a recent gas service
Igniter failed or wire disconnected
Flame sensor coated with carbon (false 'no flame' reading)

How to Fix It

Check the gas valve at the heater.

Look for a yellow or red handle on the gas line right at the heater.
It should be parallel to the pipe (open).
If it's perpendicular (closed), turn it parallel.
Try igniting again.
Test another gas appliance.

Light your gas stove or run your gas dryer.
Do they work normally?
If they don't, the issue is house-wide — your gas supply is interrupted.
Call your gas utility.
If they work, the issue is at the heater itself.
Check for recent gas service.

Has anyone worked on your gas line recently — utility, plumber, new appliance install?
Air gets into gas lines during service and takes a few ignition attempts to clear.
Try Code 11 reset 3–5 times in a row; sometimes the air bleeds through and ignition succeeds.
Reset the heater.

Press the on/off button on the front panel.
Wait 30 seconds.
Press it again.
Run a hot tap.
If Code 11 returns immediately, you've ruled out a transient issue — call for service.
Call a licensed gas installer.

If the gas supply is fine and Code 11 persists, the issue is internal — igniter, flame sensor, or gas valve.
This is licensed-installer work.
Most repairs are 100–250 USD parts plus labor.
Don't try to access internal gas components yourself.

Frequently Asked Questions

Can a propane tank running out cause Code 11?

Yes — and it's one of the most common causes for propane Rinnai installations.
Check your propane tank gauge.
If it's below 20%, that's likely your Code 11.
Refill the tank, give it 10 minutes for the gas to settle, then try ignition again.

How often should the flame sensor be cleaned?

Every 1–2 years of regular use.
Carbon builds up on the sensor and eventually insulates it from detecting the flame correctly.
The igniter fires fine but the unit thinks ignition failed because no flame is sensed.
A licensed installer cleans this in 10 minutes during annual service.