Water Heaters - Gas water heater t-stat

I have an older Richmond 5V40-7 40 gallon Natural Gas Water Heater with a Robertshaw 66-136-308 R110RTSP Thermostat. The pilot light went out, so I tried to light it. It would not stay lighted. I replaced the thermocouple, but that did not work. I guess the t-stat needs to be replaced. I would like to replace the entire heater, but money is a little short right now. Where can I find a replacement t-stat, or should I bite the bullet and buy a new one? Its a 6 year heater and its been in service for at least 10 years and maybe more.

With ten years on the heater you are just tossing good money in a hole trying to replace the thermostatic gas valve. The thermostatic gas valve is a significant portion of the cost of a new water heater.

Just my opinion.

Guessing doesn't cut it on parts replacements.


I'd say the odds are a good deal higher that the pilot orifice and pilot burner need cleaning and replacement that that the thermostat needs to be replaced. It's rare for the gas valve magnet to be so bad it wont hold when properly energized.

There could be other possible problems as well.

My advice: quit guessing and have a competent repairman inspect the equipment.

What does the pilot flame look like? Does it cover the end of the t-couple? You'll find that the thermostatic gas valve is a lot more expensive than may have thought.