Question
Yesterday my water heater went out and didn't come on, so I replace the thermocouple and the gas valve and the pilot now wont stay lit, but the old thermocouple was shorter than the new one, been the new thermocouple longer than the old one could that be why the pilot doesn't stay on?

Answer
The length of the thermocouple has nothing to do with the problem you're having. The longer thermocouple is the universal type with longer lead. Just uncoil as much lead as you need for the installation, then roll the excess in a tight roll and tuck it behind your gas tube.

I suspect that you didn't install the thermocouple properly. There are other possibilities though but if you didn't install the thermocouple properly against the pilot, it wont heat and open gas control valve.

I suggest that you do the following:
1. Make sure that the end of the thermocouple is raised at least 1/4 inch above pilot lit to heat properly.  Use a pair of pliers to bend pilot and thermocouple 1/4 closer to each other
2. While igniting the pilot, press down and hold the pilot button for 30 seconds. Pressing down and holding the button on gas control valve for 30 seconds allows the gas to enter pilot to heat thermocouple.

Other Common Problems Why Pilot Wont Stay Lit

• No gas
• Low gas pressure
• Blocked pilot line
• Faulty thermocouple - note that some thermocouples may have factory faults. So the one you just bought could be faulty.
• Faulty thermostat
• Air in gas line
• Moth and dirt in gas line...