"Jeff" wrote in message
...
I have not been able to keep my water heater pilot lit since I turned on my
AC. It might stay on for a day at most. The plumber suspected downdraft.
The Chimney sweep found nothing. When the heater is heating water there is
a powerful updraft through the chimney.

The downdraft is when the heater is NOT running. Air can get sucked down
any opening.


The sweep said I should have the thermostat replaced.

Let him sweep the chimney, not fix gas appliances.



A previous poster suggested taking off the gas lines from the valve and
blowing them out, maybe that is next?

Blow them out? What do you expect to find in them aside from gas? If the
line was clogged so much that a pilot would not operate, surely the main
burner would be starved. It works when the AC is not running. Think about
the cause and effect of this.

Go back to the original problem again. The pilot goes out when the AC is
on.

Does the AC affect the water heater thermostat? NO
Does the AC use the gas line in question? NO
Does the AC draw air from the same areas the water heater is in? YES
Does the blower cause a negative pressure in that area? Very POSSIBLE
Would a negative pressure cause a downdraft in the chimney? YES

Check that the return air ducts are functioning properly or if air is being
lost elsewhere to create the negative pressure in the AC area and thus, the
downdraft.