We have a 4 year old Service Select hot water heater. The pilot refuses to stay lit. We can manually light it, it will run for 1/2 hour or so, then everything shuts down, including the pilot light. What can we do?

I am not familiar with the term Service Select, since it is a gas water heater does it have a thermocouple, that is a safety device that is heated by the pilot, in case you didn't know what it is. Thermocoules have to have heat on them at all times or they will shut the gas system down. It is possible that your pilot is not burning high enough to keep the thermocouple hot therefore shuting down. It could be a draft that is blowing the flame away from the thermocouple. Or it could be a bad thermocouple.

All of the above applies to a heater with a thermocouple.