Pilot light won't stay lit

[hoopers]

About a year-and-a-half ago, I bought a 40 gallon Envirotemp, gas hot water heater. Had a plumber install it. Model number is G1F4034T3NV. It was manufactured 01-20-03. It has worked great until last Friday. The pilot light went out for no apparent reason and keeps going out after the tank heats. I tried leaving the covers off today when I relit the pilot (thinking it may not be getting enough air to stay lit. It still goes out. It is a bit stubborn to relight also. When I first lit it tonight, it burned all yellow flame, and then switched to blue eventually.

[hoopers]

I went down and watched that pilot light, when the burner goes off, the pilot light goes out. Any ideas?

[Ejbogusch]

Two problems come to mind and they are gas pressure or combustion air. Lack of combustion air is the most common so lets start here. If your heater has a sealed front burner then look for a screen or flame arrestor. You will want to take and blow out this area to make sure the air intake is clean. If the burner area is open then at the bottom will be a radiation plate or a metal cover covering the bottom of the heater. Their should be a 3/4 inch gap between the plate and the bottom of the heater. Many times this cover warps blocking the air flow. If this is the case you can shim it up with washers.

If it is gas pressure you will need to check this on the output side of the control valve. Around here the gas company will do this for free.

[hoopers]

I left both the silver cover and the outer cover off last time I lit it so I could see what was going on. So I know it is getting air. I will call our gas company tomorrow to talk to them. They are usually pretty helpful here, as well. Thanks for the input.