Ok, here's where I am.

I could restart the pilot and heat the water, but it wouldn't continue to heat. So, I replaced the thermocouple. No change in performance. Then, I replaced the gas control valve. As far as I can tell, the did not change anything either.

Pilot light is blue and flame from the burner is blue.
It's an electric start, gas water heater. Does the pilot stay lit, or will it re-light itself when heating again?

When I drained the tank to replace the gas control valve, it wouldn't drain all the way. I then noticed a lot of calcium and/or lime build up around the copper "nipple" that extends off the back of the control valve into the water chamber. Could there be so much calcium/lime build up that it's interfering with the thermostat?

Lastly, the water heater is only 2.5 years old. What else should I be doing? Thanks!!

Can you let us know what make and model the w/h is. Is it a side vent water heater, is the vent pvc? Please let us know, and if you could take a picture of the water heater(the more pics the better, but definitely need one of the gas valve and the top of water heater)

It's a State Select 50 gallon water heater. I think Ferguson bought out state, fwiw. Ill try and get some pics.

I'll post some pics tonight but in the meantime, should the pilot stay lit?

When I said electric start, I don't know if that's the correct description. You light the pilot with the electric spark ignitor on the gas control valve. There is no AC running to the heater.

Hi QuinLA:

My guess is that the VAPOR SWITCH is causing you issues here...

Read the instructions that should be attached to your water heater.. it will show you the vapor switch in detail.

The air filter/door at the very base of the unit cannot be blocked with dust/lint, etc... this would cause the vapor switch to disconnect the unit. Have you, by chance, remodeled and closed off air circulation/flow to the area that the water heater is in? Reduced air for combustion could cause the vapor switch to kick the pilot out, too.

If you are handy you could try to BYPASS the vapor switch by clipping the two wires together... then relight the pilot with the ignitor and see how all goes.

If bypassing the vapor switch works then you will need to replace the vapor switch... but that will not be easy to do as these are not readily available for the consumer... ;)

Anyway, read up on the switch... let me know what you think...

MARK

Hi QuinLA:

My guess is that the VAPOR SWITCH is causing you issues here...

Read the instructions that should be attached to your water heater..it will show you the vapor switch in detail.

The air filter/door at the very base of the unit cannot be blocked with dust/lint, etc...this would cause the vapor switch to disconnect the unit. Have you, by chance, remodeled and closed off air circulation/flow to the area that the water heater is in? Reduced air for combustion could cause the vapor switch to kick the pilot out, too.

If you are handy you could try to BYPASS the vapor switch by clipping the two wires together...then relight the pilot with the ignitor and see how all goes.

If bypassing the vapor switch works then you will need to replace the vapor switch...but that will not be easy to do as these are not readily available for the consumer...;)

Anyway, read up on the switch...let me know what you think...

MARK

Thanks for your response. I just looked over the manual and didn't see anything about the vapor switch??

What do you mean by "electric start" ?

State w/h's have pilot that is constantly ON.

Ok, now I read rest of your posts and see what you have. It is like BBQ ignator, correct..

As per new Code, these heaters have enclosed burning chamber. However, there are small vents on side of the heater. Make sure these vent are clean and unobstructed. It sure looks like you don't have oxygen supply going to the heater killing the pilot.

Yes, it's like a BBQ ignitor, sorry for the confusion.

I haven't had time today to mess with it too much but I see the air intake, there isn't any kind of screen on that (it's at the bottom front of the heater), is there a screen inside there somewhere I should "attack".

Yes, it on the bottom of the heater. It may have dust, lint, and other debris in it. Take vacuum cleaner and clean it well. You can also open the burning chamber and see if the heater will function w/o the sealed door attached.

I just looked at what I assume are the intake vents and can't find any kind of screen. There is some kind of pan above this chamber but no screen. I'm pretty sure this is the intake vent. I lit the burner then held a lit match next to the opening and it would draw the flame inwards.

Good idea about opening the door to the burning chamber. This will either pinpoint the problem or eliminate a possible cause.

The inner door to the chamber can't be removed because the burner assembly is connected to it via the gaskets that hold it and the thermocouple in place. I've opened it as much as I can and lit the burner. The burning sound sounds like it did before all of this, so I'm keeping my fingers crossed.

If you will use a long handled brush that is flat enough to go under the water heater you can insert it under the heater with the bristles up. There is a filter under the heater ( it is not the one that you can see on the front side of the heater) this on is right in the middle of the heater on the bottom. Brush this area and then vacuum it out as good as you can.

One other way you can try is to disconnect the vent from the top of the heater, use a shop vac with lots of power and attach it to the top of the heater where the vent connects, turn on the vac and blow down through the heater, Now remove the vac from the top and vacuum at the bottom as well as you can.

Someone suggested taking the door off and taking the sealed opening off, this will let your heater burn but it will void your home insurance if something was to happen, such as a fire.

Let me know if this helps.

Opening the door seemed to work. The tank was heated, the burner went off and the pilot remains lit. At least now I know it is an obstruction of air somewhere and I will look again for the filter and clean as suggested. In the meantime, I can wash dishes, take a shower then shut down the unit until I can go at it again. Thanks again to everyone!!

You can also use an air compressor with the right air chuck(one that will fit in the air intake and reach the center of water heater and curves upwards at the tip) It sounds like the air intake filter was not installed during water heater installation. So the honeycomb filter in bottom center of water heater is most likely plugged. You just need to get it cleaned, one way or the other. I have found compressed air works the best, also vacuum after hitting it with the air. I have posted a pic of the honeycomb filter. Yours will look like one of the round ones. Usually I see problems with these when they get wet. Did you have any moisture problems recently in you house near the water heater? Please let me know if this helps. You can also hit the filter with air from the top side.