Rheem Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater 4 FLASH Error Fix: Temperature Exceeded High Limit

Error code 4 FLASH on the Rheem Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater means: Temperature Exceeded High Limit. The water temperature has exceeded the gas control valve high limit threshold, causing a safety shutdown. This is a potentially dangerous condition that indicates the water may have been heated well above the set temperature. The most likely cause is a gas valve that is stuck partially open — allowing gas to flow to the main burner even when the thermostat portion of the valve should have shut it off. To verify: set the thermostat to its lowest setting (VACATION or lowest temperature mark). If the main burner continues to fire at this setting, the gas valve is stuck open and must be replaced immediately. Do NOT continue to use the water heater with a stuck gas valve — it can cause scalding-temperature water and tank failure. Call a licensed plumber.

The most successful fix is "Replace Faulty Gas Control Valve" (hard difficulty, ~90 minutes). Estimated DIY cost: $0-$20. HomeMD has 2 community-ranked fixes for this error.

This error is rated critical severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Replace Faulty Gas Control Valve") is rated hard difficulty and takes about 90 minutes. Tools needed: Phillips screwdriver, Adjustable wrench, Leak detection solution, Multimeter.

DIY cost: $0-$20. Professional repair typically costs $300-$450. Many homeowners save money by trying the top-ranked community fix first.

The Rheem Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater has 8 other known error codes, including: 1 BLINK / 3 SEC (Normal Operation), 2 FLASH (Thermopile Voltage Low), 5 FLASH (Temperature Sensor Failure), 7 FLASH (Gas Control Valve Electronics Failure), 8 FLASH (Insufficient Thermopile Power), and 3 more.

Error code 4 FLASH also appears on 2 other Rheem models: Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace, Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace. The fix may vary by model, so check each model's specific page for tailored repair steps.