Rheem Water Heater Code 11: What It Means and How to Fix It

By Dan Mercer · Published October 5, 2026 · Updated October 5, 2026 · Codes covered: 11 · Sources

Verify in your manual: Rheem's owner manuals give one owner fix for code 11 (gas shut-off valve not fully open). The No Ignition name comes from the error code list on the support page of Ruud, Rheem's sister brand. Codes vary by series; check your Use and Care manual.

Code 11 on a Rheem tankless gas water heater means the burner didn't light, so the heater shut down and you get cold water. Rheem's own fix for owners is simple: make sure the gas shut-off valve at the heater is fully open, then reset. If that doesn't clear it, the rest of the job (gas pressure, gas line, igniter) belongs to a licensed technician.

This 3-minute fix saved 0 homeowners a technician visit this month.

What the 11 code means

Rheem's tankless Use and Care manuals (both the non-condensing RTG and the condensing RTGH series) list one cause for code 11: "The gas shut-off valve is not fully opened." The solution they give is "Check shut-off valve and open completely."

Ruud, Rheem's sister brand, publishes a tankless error code list on its customer support page that names code 11 "No Ignition." That's what's happening. Rheem tankless heaters have no pilot light. When you open a hot tap, the heater sparks and tries to light the burner. If it can't, it stops and shows 11 on the remote.

Look-alike codes that mean something different:

• Code 12: Rheem's manuals link this one to an interruption in gas service, or LP gas running low on propane models. Many of the same checks apply.
• Codes 90 or 99: the air intake or vent exhaust may be blocked.

Rheem has several tankless product lines, and the code charts differ between them. Keep your model's Use and Care manual handy and check its "Service Error Code Chart."

Likely causes (most common first)

1. Gas shut-off valve not fully open. This is the cause Rheem lists. It often happens after other work in the house.
2. No gas reaching the heater. Gas service is off at the meter or interrupted, or a propane tank is empty.
3. Air in the gas line, usually after a new install or gas work. Ruud's list includes bleeding air from the gas lines, which is an installer's job.
4. Wrong gas pressure, or an undersized gas line, meter, or regulator. Ruud lists all of these for code 11. Rheem's troubleshooting chart sends low gas pressure to your gas utility or gas contractor.
5. Wrong gas type. Rheem warns that a natural gas heater won't work safely on propane, and vice versa.
6. Poor electrical ground. Ruud lists grounding among the code 11 checks.
7. Igniter, igniter wiring, or gas valve problem. These are internal parts that a technician has to test.

How to fix it, step by step

Work in order. Try a hot tap after each step, and stop the moment you smell gas.

1. Do Rheem's reset. Close all hot taps, turn the heater off at the remote, wait about 5 minutes, turn it back on, and open a hot tap.
2. Open the gas shut-off valve completely. It's on the outside of the water heater.
   • If it was closed, follow the Operating Instructions label: turn off power, close the valve, wait 5 minutes and smell for gas, then open the valve and restore power.
   • If it won't turn easily, don't force it. Call a technician.
3. Power-cycle the heater. Unplug it for about 30 seconds, plug it back in, then try a hot tap.
4. Confirm you have gas. If no gas appliance works, call your gas utility or propane supplier.
5. Think about recent gas work. After a new install, meter change, or propane tank swap, air in the line is a likely cause. Call your installer. Don't loosen fittings to bleed the line.
6. Check the plug and breaker. The heater should be plugged into its grounded outlet, with the breaker on.
7. Write down the code and call for service if 11 keeps coming back. That's Rheem's own advice. Everything past this point means live gas or live voltage.

Test the part

The parts behind code 11 (igniter, gas valve, burner) sit inside the cabinet, right at the gas controls. Testing them isn't a homeowner job. Rheem warns that removing the front cover exposes you to live electricity. Here's what you can check safely.

1. Unplug the water heater and turn off the gas. Pull the plug (or switch off the breaker on hard-wired outdoor models). Then turn the gas shut-off valve clockwise to OFF.
2. Look over the power cord. Check for cuts, scorch marks, or a missing ground pin.
3. Look at the gas connection from the outside only. Check for a crushed or kinked line. Don't tighten or loosen anything. If something looks wrong or you smell gas, leave and call the gas supplier.
4. Check the vent and air intake. From outside, make sure the vent termination isn't blocked by snow, leaves, or nests. Rheem says the air intake needs 12 inches of clearance.
5. Look for water damage. Rheem says a heater that has been in a fire or flood, damaged, or under water should be shut off at the gas valve and not used until a qualified service person checks it.
6. Don't open the cabinet to test parts. Igniter and gas valve checks need live voltage and gas, so no meter readings are given here.

When you're done, follow the Operating Instructions label to turn the gas back on and restore power.

Safety notes

When to call a pro

Stop and call a licensed plumber or gas technician if:

• Code 11 comes back after the reset, with the gas valve fully open and other gas appliances working.
• The heater is new, was just converted, or the gas was recently worked on. Bleeding the gas line and checking gas type are installer jobs.
• You suspect low gas pressure or an undersized gas line. Measuring pressure needs a manometer and a licensed gas pro.
• The fix would mean removing the front cover. The igniter and gas valves sit behind it, next to live wiring.
• You see rust, scorching, or water damage on or under the heater.
• The heater is under warranty. Have your model number, serial number, and installation date ready.

Rheem's contact page lists water heating support at (800) 432-8373, Monday to Friday, 7 a.m. to 7 p.m. Central. Your Use and Care manual also asks you to start with your installer or a licensed service agent.

FAQ

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