Rheem gas water heater status light: 10 red blinks every 3 seconds (Low NOx models)
Chamber temperature shutdown: the combustion chamber got too hot and the heater shut down. The same manual says the heater has a combustion shut-off device that stops it when combustion conditions are unsafe, such as flammable vapors or blocked combustion air openings, and to contact a qualified service technician if that happens. This code is only in the Low NOx manual.
If you smell gas
Stop: do not relight or troubleshoot anything. Rheem’s own words (first page of both Use & Care Manuals, AP23060 and the Low NOx AP23698):
- Do not try to light any appliance.
- Do not touch any electrical switch; do not use any phone in your building.
- Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
- If you cannot reach your gas supplier, call the fire department.
- Do not return to your home until authorized by the gas supplier or fire department.
Calling from a neighbor’s phone means leaving the building first.
What you see: 10 flashes, then a pause, repeating. Applies to: Rheem residential Low NOx (10 ng/J, SCAQMD Rule 1121) atmospheric gas water heaters, 29 to 55 gallons.
What it means
The manual’s wording: “Ten (10) blinks every three (3) seconds — red” — Rheem Low NOx models (AP23698).
Chamber temperature shutdown: the combustion chamber got too hot and the heater shut down. The same manual says the heater has a combustion shut-off device that stops it when combustion conditions are unsafe, such as flammable vapors or blocked combustion air openings, and to contact a qualified service technician if that happens. This code is only in the Low NOx manual.
What Rheem tells the owner to do
Rheem’s manual gives the owner no step of their own for this code: call for service.
Rheem’s chart gives no owner step for this code: it says to see “If You Need Service”.
semiatic gives no repair instructions of its own. The steps above are only the ones Rheem addresses to the owner in its manual.
When to call a qualified service agency
Rheem’s manual: “CAUTION: For your safety DO NOT attempt repair of gas piping, Combination Gas Control (Thermostat), burners, vent connectors or other safety devices. Refer repairs to qualified service personnel.” For service it says to contact your installer, plumbing contractor or previously agreed upon service agency first, then Rheem’s national service department on 1-800-432-8373 with the model and serial number from the rating plate.
Source
Rheem’s own manual, read on the date shown.
- Rheem Manufacturing Company: Use & Care Manual with Installation Instructions — Water Heaters, Residential Gas, Low NOx Emissions (AP23698), “Gas control (Thermostat), Status Light Troubleshooting” — Rheem residential Low NOx (10 ng/J, SCAQMD Rule 1121) atmospheric gas water heaters, 29 to 55 gallons. files.myrheem.com Checked 2026-09-29.
The same pattern on other brands
The same count on another maker’s gas control can mean something else.