I have an old gas water heater that is no longer providing hot water. The thermostat has been turned up all the way to Very Hot and the water is still mildly hot at best. I have not inspected the dip tube yet, and will look at it this weekend. Assuming the dip tube is in operable shape, then I imagine the thermostat will need to be replaced. The unit is old (> 20 years) . The thermostat is model 37C73U 629. This is apparently obsolete. Is there a model that I can use to replace this or am I just going to have to replace the water heater if the thermostat is bad? In other words, if the thermostat has to be replaced, can I just get one that's close to matching, or do I have to have the same model?