Why does your gas hot water heater pilot keep going out?
- This is usually caused by a bad thermocouple. The thermocouple
looks like a thick, solid copper wire screwed into the gas valve on
the water heater. The pilot flame heats the tip of the
thermocouple, causing it to generate a minute electrical current at
low voltage, which provides power to an electric valve that
controls the flow of gas to the main burner. If you attempt to
relight the pilot burner and it refuses to stay lit when you
release the button on the gas valve a minute, or so, after the
flame has been lit, the thermocouple is the most likely cause.
Replacement thermocouples are readily available from most hardware
stores and can be replaced by the homeowner, using simple tools, by
following the instructions on the package.
- Another cause of the problem could be a lack of air to the
combustion chamber. Newer water heaters require more volume of air
due to the addition of a heat sensitive diode to the thermocouple.
Not enough air flowing through the combustion chamber to carry the
heat up through the flue causes heat build up, which kills the
thermocouple. On my water heater, I could light the pilot and the
water heater would burn for 20 minutes or so and shut off. The fix
included routing the flue straight through the roof and opening
floor to allow more air into the water heater compartment.
- Another possible culprit may be water-heater vent height above
the roof. In some situations this may periodically result in a
downdraft that could cause the pilot light to go out. If this is
the case adding to the vent height may help. Note: building code
states that the B vent required height is based on the roof pitch
but it must be 2 feet higher than any portion of the building
within 8 feet of the vent.
- Make sure the vent cap isn't missing or rusted through on the
roof, it will cause drafts and wind to blow out the pilot.