Rheem water heater burner cycles on and off rapidly, causing fluctuating water temperature

Safety first: Turn OFF power or gas before adjusting internal components.

• Check thermostat contact: Ensure the thermostat is firmly against the tank surface (electric) or properly sensing tank temperature (gas control).
• Descale (tankless): Perform a full descaling flush to improve heat transfer and reduce overshoot.
• Increase flow (tankless): Avoid using very low flow rates that cause the unit to cycle. Open taps more fully or use fewer low-flow fixtures simultaneously.
• Replace faulty thermostat: If temperature swings remain large, replace the thermostat or gas control valve.