I have an Envirotemp model G1H4040T3NV water heater that has a problem of the pilot light not staying lit. I previously replaced the thermocouple and that fixed the problem for a few months, but then it started not working again. I tried another thermocouple, but it did not do it this time. I found a control gas valve that looks exactly like the one I have on there, but the part numbers are different. They are both Robert Shaw valves, and the original is a part number 66-178-335, while the new one is a 64-LF-376. What is the difference, if any?