I have a state select water heater and I changed out my thermalcouple and replaced the gas valve. The pilot would not light. so now the pilot light does stay on but goes off once in awhile. There is no draft. It appears to go off at times after the main burner lites . It gets frustratiing. Any advice?

The draft could be only occasionally prsent, most of the time it is a down draft. Many down drafts are caused by whole house fans and bathroom exhaust fans.