thank you for your reply. I'd like to post a picture, but I can't reduce the image size. The pilot and burner are blocked by a metal plate through which the gas and electric pass, in a way that I assume would make it hard to take the plate off. But I suppose it can be done and I'm handy enough to do it. I've successfully replaced thermocouples before, and unless you have other suggestions I suppose that's what I should do here. We just had what is for us a hard freeze which means it got down to about 25 F, and that was when the pilot failed. The water in the house wouldn't run for two mornings until the temperature got high enough to thaw the ice. Also the tank is in a separate shed that's about 18 in outside the exterior of my house. I bought this place that way, I didn't build the water heater shed like that. The tank doesn't seem to be leaking water at this time. Any further suggestions? I'll try the thermocouple.