Rheem Water Heater Error Codes: Tankless Codes and Tank Flash Codes

Tankless or tank: which codes you are looking at

The two product types use different codes, and the same number can mean different things on each. A "12" on a Rheem tankless means the gas supply was interrupted. On a Rheem PowerVent tank with a display, 12 means a low flame signal. Check which kind of heater you have before you read either table.

• Tankless (wall-hung box, no tank): read the number on the LED display and use the first table.
• Gas tank: count the flashes of the small light on the gas control, then find your control type in the tank section.

The model number is on the rating label. On the tankless models below, Rheem says it is on the top label on the right side of the water heater.

How to clear a Rheem tankless error code

Rheem's tankless use and care manual (AP22009) gives a three-stage routine on page 76. When an error code shows:

1. Turn off all hot water faucets.
2. Press the POWER ON/OFF button to turn the water heater off.
3. Wait about 5 minutes, then press POWER ON/OFF again.
4. Open a hot water faucet and check the display.

If the code is still there, close the faucet, turn the heater off, unplug it for about 30 seconds and plug it back in. Then do the owner check in the table below and restart. If the code still shows after that, note the number and call for service. Rheem adds that if your code is not in the chart, you should turn the water heater off at once and call for service.

Rheem tankless error code table

These are all the codes in the Service Error Code Chart on page 77 of Rheem's AP22009 Rev 04 manual, which covers Rheem's non-condensing 199,900, 180,000 and 160,000 Btu/h tankless gas models (indoor direct-vent RTG-95DVL-3, RTG-84DVL-3 and RTG-70DVL-3, plus the outdoor versions), as of October 2026.

If your Rheem tankless has a different model number, for example a condensing model, use the chart in its own manual rather than this one. Rheem's National Service Department number in this manual is 1-866-720-2076.

Code 11: the gas valve is not fully open

Rheem's only owner step for code 11 is to check the gas shut-off valve to the water heater and open it completely. Then run the restart routine above. If the valve is open and 11 returns, call a technician.

If you smell gas, do not touch the valve or the power button. Rheem's manual says not to touch any electrical switch or use a phone in the building, and to call your gas supplier from a neighbor's phone. Leave the house first.

Code 12: gas interrupted or low propane

Rheem gives two causes. On natural gas, the gas service has been interrupted, and the manual says to contact your gas utility company. On LP models, the propane may be running low, and the fix is to refill or replace the LP container. Once gas is back, restart the heater with the routine above.

Codes 90 and 99: blocked air intake or vent

These mean the air intake or the vent exhaust opening may be blocked. Rheem says to remove any blockage and notes that the air intake needs 12 inches (30 cm) of clearance from any obstruction. Its care section also tells owners to check the air intake and vent outlet for blockage or debris. If the vent pipes at the termination are not connected properly, that is a job for a dealer or licensed technician.

Code P1: not enough water flow

P1 means too little water is moving through the heater for it to fire. Rheem's fix is to increase the water flow from the fixture. Its troubleshooting chart for low or no hot water also lists a clogged water filter and a dirty fixture aerator, and says the main burner goes off when the incoming water volume is too low.

Rheem says to clean the water filter monthly. Turn off the heater and disconnect the power, turn off the water supply and drain the unit as the manual's draining section describes. Then unscrew the filter from the base of the cold water inlet line, rinse it under running water (a soft brush for heavy sediment) and screw it back in until snug. Do not tap, force or overtighten it, because that can deform the filter.

Code 88: the maintenance reminder

Code 88 is not a fault. It is an optional reminder, off from the factory, that can be set to come on after 500, 750 or 1,000 hours of combustion. Rheem highly recommends flushing the heat exchanger and replacing the water treatment filter, if you have one, before you clear it. To clear 88 after the maintenance, per page 79 of the manual:

1. Turn on the remote control.
2. Close the gas and water shut-off valves to the water heater.
3. Press DOWN repeatedly until the lowest temperature shows on the display.
4. Press and hold DOWN and UP together for 5 to 10 seconds.
5. Open the gas and water shut-off valves again. If 88 is still shown, repeat the steps.

For more on clearing faults across brands, see our guide on how to reset a tankless water heater.

Rheem gas tank water heater status light codes

Rheem tank heaters do not share the tankless codes. The flash codes below come from two of Rheem's water heater technical bulletins, which are written for service technicians. Use them to tell a technician what you see, not as repair steps. Rheem's bulletin 1425 on the White-Rodgers thermostat control used on standard atmospheric tanks lists no flash codes; its troubleshooting points to the thermocouple, gas valve and pilot outage bulletins.

Vesta gas control (standard atmospheric and Ultra Low NOx tanks)

Rheem's bulletin 1442 on the Vesta control describes a thermopile-powered gas control with an LED. A steady light means the knob is set to Off. One short flash every three seconds is normal. A fault flashes one short flash per second for the code number, then pauses three seconds and repeats.

Rheem lists 3 as not used and 6 as used only with an accessory module. For code 4, the bulletin's reset is: power up in Pilot, wait for the fault code, turn the knob to VERY HOT for 10 seconds, then HOT for 10 seconds, then PILOT for 10 seconds. The code clears, and Rheem says to set the knob no higher than 120 °F. If 4 comes back, the water is overheating for a reason a technician needs to find.

PowerVent with the Honeywell electronic control

Rheem's bulletin 1627 for the PowerVent ESII covers power-vent tanks with a Honeywell electronic gas control. A short flash every four seconds means idle, and a bright-dim "heartbeat" means it is heating. The number in brackets is the code that models with a display show.

Rheem says several of these lockouts clear only when power to the control is cycled, but the causes Rheem lists, such as gas supply pressure, the igniter or the venting, are technician work. Code 47 needs care: Rheem's manuals say never to store or use gasoline or other flammable vapors and liquids near a gas water heater. If you smell gas rather than fumes, leave the house and call the gas supplier from outside.

Which Rheem models this page covers

The tankless table is from Rheem's AP22009 Rev 04 use and care manual for its non-condensing tankless models. The manual's warranty section names Rheem, Ruud, Richmond, Paloma and EcoSmart residential tankless heaters, but Rheem does not say in that manual that every brand or series uses this code chart, so match your own manual first. The tank tables are from Rheem bulletins 1442 (Vesta control) and 1627 (PowerVent ESII). Rheem tanks with a touchscreen display, such as its super high efficiency gas models, show alarms on that screen instead, and we have not covered them here.

For faults with no code, such as rusty water or a leak, see our list of common water heater problems. Other tankless brands: Rinnai error codes and Navien error codes.