Need help from the brain trust! One of our single family rental houses (built in the 90's) has a gas water heater. We had to replace the old one (Bradford White) about 12 to 18 months ago. The new one (State) has consistently had problems with the pilot light going out. It's gotten worse lately, and won't stay on more than 30 minutes before going out. State sent our plumber a new gas valve thinking that would fix the problem. He just installed it and the pilot light is still going out. State is now saying that the water heater is a "low nox" (high efficiency) unit, and it's probably not getting enough fresh air flow. The WH is installed in an interior laundry room, so there's not much of a way for us to give it more air other than open an exterior window, which of course isn't a good option long term. (Just to test their theory, we plan to ask the tenant to open the window overnight and see if that helps). Unfortunately, the house uses this water heater for hot water AND for heat (an Apollo system), so we've got to figure this out for both hot water and for heat. Has anyone run into problems with gas water heaters that are inside the interior of the house? Any ideas/suggestions/comments would be most appreciated!!!

You need to test the thermocouple to see if it generating enough power/current to keep the gas safety valve open -- should read about 25 millivolts. You can also look at the pilot flame to see the size and color. If too small or the wrong color, the pilot gas tube to the orifice may be clogged and needing to be blown out or cleaned. I have a tester meter and tester magnetic valve tester.

If the pilot is good and the voltage is right, then it has to be the thermostat control valve. Or if your gas in lie has a moisture trap, you'll need to empty it out and check for moisture in the input gas supply -- this is before the gas turn-off cock.

ALSO check the vent pipe that goes to the roof, it may have a birds nest or rat/mouse nest too.

I have had problem from very small amount of debris in the small gas tube. Cleaned it out and problem was gone.

Other issue was as described above there is even a code requirement for sufficient combustion air.

Plumber should know all about those things. Maybe need better plumber.

This wasn't on a water heater but high efficiency furnace. The pipe going outside to vent.

Our furnace started cycling on and off last year-- after checking everything I could think of my son said -- he thinks the pipe is plugged or broken. So we start looking to see if any damage. Pulled the end cap off-- the one to keep birds out and there it is-- a WASP nest-- inside the pipe. Yanked it out and bam the furnace starts working. This year furnace started same thing-- went right to that pipe and found another WASP nest.