I too had a service agreement; called in because the pilot light on my water heater would not stay on. A plumber came within one hour of my call. He looked at the water heater and told me that I needed to replace the gas valve and that it would cost approximately $475 for the work to be done (labor only) and it would take an hour. I was not happy with this and decided to have a second opinion.
Turns out the most common problem in these circumstances is the thermocouple -- in our case the thermocouple did not even need to be replaced -- simply cleaned and reattached. The repairman did not bother to remove the thermocouple -- and apparently it was not cleaned during the most recent maintenance checks either. It took less than 10 minutes to fix by someone without any plumbing experience, no parts were needed. The valve did not need to be to touched.
Needless to say, I have cancelled the agreement and will not be using this company again.
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