Rheem Water Heater 6-5 flashes: Hard lockout (error 10)
Updated October 2026 · Sourced from Rheem documentation
The gas valve status light is flashing six, then five times with a three second pause. The bulletin says the control is in hard lockout. It can only be cleared by manually cycling control power.
Is it safe to keep running? No. Turn it off and get it checked. The bulletin lists low gas supply pressure, carbon on the electrode, igniter wire damage and pilot or burner tube restrictions as causes. These are gas and ignition parts for a qualified technician.
6-5 flashes at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| 6-5 flashes Gas valve status light: six flashes, then five flashes, then a three second pause. Display models show 10. | Hard lockout (error 10) | Rheem PowerVent ESII gas tank water heaters with Honeywell electronic gas control (gas valve status light flash codes, and display codes on electronic control models) |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Turn the water heater off at its power switch or unplug it, wait a minute and power it back on once. The bulletin says these lockouts clear only by manually cycling control power.
- If the same flash pattern returns, do not keep resetting it.
🛑 Stop and call a licensed pro if
- The bulletin lists low gas supply pressure, carbon on the electrode, igniter wire damage and pilot or burner tube restrictions as causes. These are gas and ignition parts for a qualified technician.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Codes for flame failure, overheating, venting or the control board that return after one reset.
- Water leaking from the heater, the relief valve discharging, or scorching around the burner area.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any Rheem code
- Write down the exact code shown on the controller or the number of status light flashes.
- Turn the water heater power off and back on (or press the reset button the manual describes) once. If the code comes back, stop resetting.
- Make sure the gas supply valve to the heater is open and other gas appliances in the home are working.
- Make sure the cold water supply valve is fully open and hot water taps are not partly closed.
- Look at the outside vent terminal for snow, ice, leaves or anything blocking it (look only).
Source: Rheem Technical Service Bulletin 1627, PowerVent with Honeywell Electronic Control, p. 2. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
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