8 flashes = Combustion air / intake blocked. The combustion air switch detected restricted intake air flow. On State FVIR-equipped units, this almost always means a clogged intake screen at the base of the unit.
The #1 cause: clogged intake screen
State FVIR (Flammable Vapor Ignition Resistant) gas water heaters draw combustion air through a fine mesh screen at the base. The screen prevents flammable vapors (from spilled gasoline, paint thinner, etc.) from reaching the burner. Over time, the screen accumulates:
- Lint from laundry rooms
- Pet hair
- Dust and dirt
- In rare cases, paint over-spray or construction debris
How to clean the intake screen
- Turn the gas knob to "Off" for safety
- Look at the bottom edge of the unit — the screen is the perforated metal ring at the base
- Vacuum the screen thoroughly with a brush attachment
- For heavy buildup: use compressed air (gas off) or a soft brush
- Don\'t use water — leaves residue that re-attracts dust
- Turn gas back on; relight pilot
- Monitor LED — should return to 1 flash within minutes
This 5-minute task resolves 80% of 8-flash issues. Plan to clean the screen annually.
Other causes (less common)
- Combustion air switch failure: switch stuck open. Replace switch
- Wiring fault: open circuit between switch and gas valve
- Heavy carbon buildup on burner: requires burner cleaning by installer
- FVIR sensor fault: false positive vapor detection — sensor replacement
If cleaning the screen doesn\'t resolve
- Verify combustion air supply to the install space (50 cubic feet per 1,000 BTU/hr in confined spaces)
- Check that nothing is blocking the area immediately below the unit (storage boxes, etc.)
- Call State support — combustion air switch replacement is dealer-installed
Why the intake screen is required
The FVIR design is a 2003 federal mandate. The screen prevents combustion of flammable vapors that might accumulate near the floor. This is a safety feature that\'s worked exactly as designed in many home garage installs since.
Bottom line
Clean the intake screen — fixes 80% of 8-flash issues. 5-minute DIY. Annual cleaning prevents recurrence.