Ruud tankless water heater shows error code 13; unit may shut down shortly after ignition.

Safety first: Turn OFF power and gas. Combustion issues can lead to carbon monoxide; ensure adequate ventilation.

• Step 1 – Confirm gas type and setup: Verify the heater is configured for the correct gas (NG or LP) and that any conversion kits were properly installed.
• Step 2 – Inspect venting: Check that vent pipe size, length, and termination meet Ruud specifications. Look for sags, dips, or disconnections.
• Step 3 – Clean burner and heat exchanger: Remove the burner assembly if accessible per the service manual. Vacuum dust and debris from burner ports and around the heat exchanger.
• Step 4 – Clean flame rod: Remove and clean the flame rod with fine sandpaper. Reinstall and ensure good electrical contact.
• Step 5 – Professional combustion analysis: If code 13 persists, a technician should perform a combustion analysis and adjust gas pressure or replace components as needed.