On the covered Rheem tankless gas water heater, 80 means error: a gas control valve malfunction. Rheem's pocket manual says the unit detected flame when demand for hot water ended and the unit turned off. First, turn off the gas at the shut-off valve.
Differential
Likely causes of “Rheem tankless gas water heater code 80”, and how to tell them apart
- 1
The gas control valve is not closing fully
What separates it Code 80 shows and the burner flame is still present after the unit stops
How to confirm Do not investigate near the unit; call the gas company or a technician
- 2
A solenoid valve that stays open
What separates it Code 80 returns after a reset
How to confirm A technician checks each solenoid with a meter
- 3
A flame rod that reads flame after shutoff
What separates it Gas control checks pass
How to confirm A technician measures the flame rod
- 4
A valve seat fouled by debris in the gas line
What separates it Code 80 on an older heater or after gas line work
How to confirm Debris can stop the valve seating and let gas through when it should be shut
- 5
A flame rod that senses flame after shutoff
What separates it The display shows code 80 and a technician finds the valve sound
How to confirm A flame rod that reads flame from a lingering heat source can set the code without a valve fault
- 6
Debris carried in on a new or repaired gas line
What separates it Code 80 follows plumbing or appliance work on the gas supply
How to confirm A fragment of pipe sealant or scale can lodge in the valve seat and hold it open
- 7
A power glitch during shutdown
What separates it Code 80 appears once after a power flicker at the moment hot water was turned off
How to confirm A momentary power dip during shutdown can leave the control uncertain about the valve state and report the fault
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether you smell gas
- Whether a flame is visible after the heater stops
- Whether code 81 also appears
- The model and serial number
Try in this order
0 of 11 completedWhat to do first
ReversibleTurn off the gas at the shut-off valve.
Correct only the documented fault domain
ReversibleRheem's pocket manual lists gas control valve diagnostics for a technician. Rheem's steps when a code shows: turn on a hot water faucet and recheck the remote control display. If the code stays, turn off the faucet and the water heater, unplug the water heater for about 30 seconds and plug it back in, follow the chart for your code, restart the water heater and recheck. If the code is still shown, turn off the faucet and the water heater, note the code and call for service. If a code is not in the chart, turn the water heater off immediately and call for service.
Smell for gas
ReversibleIf you smell gas, leave the area, do not touch any switch, and call the gas company from outside.
Switch the heater off
ReversibleTurn the unit off and close the gas valve if it is safe to reach.
Call for service the same day
ReversibleRheem's response is to test the solenoid valves and flame rods and replace the gas control valve.
Do not try to repair the gas train
ReversibleThe solenoid valves and the gas control valve are tested by a licensed technician with meters. Your job is to shut the heater down and keep everyone clear if there is any gas smell.
Give the service company the code history
ReversibleTell them whether code 81 also appeared and when each began. Rheem lists 80 and 81 together as a gas cut-off failure, so both help the diagnosis.
Keep the heater off until it is tested
ReversibleA tankless heater reporting flame with gas off has two possible stories: the valve leaks gas, or the flame sensor is wrong. Only a technician with a meter can tell which, so treat it as a leak until shown otherwise.
Write down what changed
ReversibleNote any recent gas work in the house, a new appliance on the same line, or a change in supply pressure. Those details help a technician decide whether to check the line before replacing the valve.
Keep the heater off, not just reset
ReversibleSwitch the heater off at its control and leave the gas valve closed until the technician arrives. Rheem treats a valve that may not shut off as a same-day issue, so a reset is not a way to keep going.
Close the gas valve if you can reach it safely
ReversibleThe shut-off valve on the gas line to the heater is the first thing to close. Do it without touching electrical switches if you smell gas, and call the gas company from outside.
Model-specific
What is true of this model and not of its siblings
- Shown as
- Code 80.
- Part named
- Gas control valve and solenoids.
Stop boundary
When this stops being a self-service repair
- !If you smell gas, leave and call the gas company from outside
- !Do not operate the heater; same-day service is the right response
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does 80 mean on a Rheem tankless gas water heater?+
Error: a gas control valve malfunction. Rheem's pocket manual says the unit detected flame when demand for hot water ended and the unit turned off.
What does code 80 mean on a Rheem tankless heater?+
Flame is detected after the gas should have shut off, so the gas control valve may not be closing.
Can I reset it and keep going?+
No. Gas codes should not be reset and ignored.
Is code 81 related?+
Rheem lists 80 and 81 together as a gas cut-off failure.
Is code 80 different from code 51?+
Rheem's heaters report several gas valve problems under different numbers. Code 80 specifically reports flame detected after the gas should be off.
Can I keep using hot water?+
No. A heater that may not shut its gas off should stay off until a technician has checked it.
Is code 80 an emergency?+
It is a lockout that needs prompt service. If you smell gas at any time, leave and call the gas company from outside.
What is the difference between code 80 and 81?+
Rheem lists both as gas cut-off failures, one for each valve in the gas train, so both numbers point at the same repair.
Does a tankless heater have a pilot light?+
No. A tankless gas heater lights its burner on demand, which is why flame after shutoff is a fault the control can detect and report.
Do I need a plumber or a gas technician?+
A technician who is qualified for gas appliances should handle it, since the repair involves the gas control valve and solenoids.
Will my hot water stop while code 80 shows?+
Yes. The heater locks out, so you will have no hot water until it is repaired or the lockout is cleared by a technician.
Could a power flicker cause code 80?+
It can raise the code once, but because the heater cannot tell a glitch from a valve that is stuck open, it still locks out and a technician checks the valve.
How long does the repair take?+
That depends on the part and the technician's schedule. Ask the service company when you book and tell them the code and the model.