Safety first: Turn OFF power and gas if you smell gas. Ventilate the area and do not use open flames.

Step 1 – Confirm gas supply: Ensure the manual gas shutoff valve to the heater is fully open. Check that other gas appliances work properly.
Step 2 – Purge air from line: After new installation or gas interruption, multiple ignition attempts may be needed to purge air. Reset the unit and try again several times, allowing it to stop between attempts.
Step 3 – Inspect igniter: Remove the front cover. Locate the igniter and flame rod. Check for cracks, heavy soot, or loose wiring. Clean the tip with fine sandpaper and ensure proper gap and alignment per the service manual.
Step 4 – Check venting: Make sure intake and exhaust are not blocked, as poor combustion air can prevent ignition.
Step 5 – Replace igniter/flame rod assembly: If cleaning and wiring checks do not help, replace the OEM Ruud igniter/flame rod assembly. Turn OFF power and gas, remove mounting screws, disconnect wiring, and install the new part.

If code 11 persists, gas pressure and valve operation should be checked by a licensed technician.

Ruud tankless water heater displays error code 11; burner does not ignite and water remains cold.

Possible Causes