I replaced my thermo coulping to my water heater and my pilot still does not stay lit, what else can the problem be. I appreciate any suggestions.

Thank you

Not to be redundant did you do this by the book?
Turn the control knob to the pilot position and immediately hold a match near the end of the pilot-light tube. Depress and hold the reset button on the gas-control valve . Remove the match as soon as the pilot lights, but keep the button depressed for about a minute or more.

If the pilot does not remain lighted, repeat all these steps. Otherwise, turn the gas cock on the control valve to the On position, set the thermostat to the desired temperature and replace the access panels.

Re lighting pilots can be a hassle mostly it takes time for gas to get to the pilot its very low pressure. Try the above and get back. Very Seldom does a gas valve go bad.

Check the thermocouple couple if its to far away from the pilot light it won't heat enough and the pilot will go out

Signed 21 Boat

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First of all, big props for using the correct terminology (i.e.water heater NOT hot water heater).

When you replaced the thermocouple did you make certain that you didn't cross thread it? It is very easy to do so without even knowing it. Also did you get it tight? It is also possible to over tighten.

In my 10 years in the propane industry, if a newly installed thermocouple (TC) isn't staying lit, then the problem may be that the tip of it is not in the right position. When you light the pilot light, the top 1/2 inch or so of the TC should be directly in the flame. If the TC is too high, then the flame is hitting it in the wrong spot and it won't stay lit. If the tip of the TC is too low, same problem. If you get the TC positioned correctly and it still won't stay lit, it is quite possible that the main control is shot. As 21 boat said, it doesn't happen very often... but it can happen.

Something else you might try... BUT BE VERY CAREFUL DOING THIS!! Locate where the pilot tube goes into the control, then take your wrench or the handle of a screwdriver and tap lightly or moderately on the side of the control. I have run into occasions where a valve inside the control has gotten stuck. If this fixes your problem it is mostly a temporary fix... and you should probably change out the control anyway. I would have a licensed plumber or gas person do this.

Hope this helps.