I went to purchase a new thermalcouple only to find I needed a left handed thread, so I called standard water heater people, they sent me a whole new heating unit, with the adapter for the left handed thread. I installed the new unit. I lit it, it was OK for about 5 minutes, then it went out. The safety switch tripped. I reset it and then the pilot wouldn't stay lit anymore. I called standard water people again. They said the only thing it could be now was the control valve. I purchased a control valve, installed it, lit the heater, and once again, after approx 5 minutes, it tripped again and shut off. I restarted it about 4 times and each time, it would trip the safety switch. Does any one know why this keeps happening?