Water Heater Pilot Won't Stay Lit

I recently had to turn off the main valve at my gas meter to cap an old buried gas line to my pool heater that rusted out and started leaking. When I turned the gas back on, the pilot lights for both my water heater and fireplace will not stay lit. I can get both to light up when I push down the pilot button, but as soon as I release it they both go out. Both were working properly prior to turning off the main gas valve. I did go ahead replace the thermocouple on the water heater but it is doing the same thing and I find it hard to believe that it is a coincidence that both appliances are doing the same thing. My gas furnace is firing up normally. What else could be the cause of this?

 

I have tried several times holding it down for at least a minute or two and it will not stay lit on either appliance. When I first turned the gas back on I was able to get the water heater pilot to stay on and it did fire up and heat the water normally. But the next morning the pilot was out and I have not been able to get it to stay lit since

 

If the thermocouple tip is not positioned in the flame, could you bend something?

 

Air in the lines? Can take a while to bleed that out with just a pilot.

 

If the pilot stays lit while you hold the button in, I wouldn't think that would be a problem.

What make and model?

 

Ive had it many times, air causes a weak wavy pilot that often doesnt have enough heat to keep the thermocouple warm.

Ive got a second story gas heater, and a range on the first floor with open pilots on the cooktop. When I shut the gas off in the winter (its a seasonal place) the gas spends all winter falling down from the second floor and leaking out the cooktop open pilots.

In spring when I go to light it, I get a week wavy pilot on the heater. Often it'll light but then go out a few minutes later and will take some time to get relit.

Just sounded similar to my issue.

 

I had the similar problem couple of days ago.
Was what I would call as strange occurence, after starting heater, heater would shut off within a few minutes but relight and continue the shutting down issue afterwards.
Following advice from many forums indicating a faulty thermocoupling, I replaced the thermocoupling with a new one and results stayed exactly the same.
Turns out the bracket holding the thermocoupling in place at the correct distance from pilot had moved a bit apparently from a couple of years of thermal expansion and contraction- in short when the first shutdown occured there was a loud "pop" as if something had broken and -yes- the bracket moved just a small amount when this occurred, causing just enough diatance to allow the thermocoupling to heat sufficiently enabling start up but after a few minutes of cooler air drafting through the vent- to feed the flame- the thermocoupler was cooling off enough to break contact.
Heater works well now even with the older thermocoupling reinstalled (had to check it's condition out of couriosity) with no issues after readjusting but this was difficult to figure out since the bracket is not adjustable. The key indicator (for me)was the fact the lighter was close enough to become red hot after the flame out and restart each time. After readjusting the bracket (accomplished by causing enough tension with the copper tubes attached to thermocoupler to allow the bracket to remain in proper positioning), the lighter end is not discolored at all after start up and thermocoupler is in the correct close distance from pilot light to enable stable operation of the unit..
Hope this helps.

 

Your gas valve was affected by turning the gas on or off to quickly. Disconnecting the gas burner and pilot assembly blowing through it and making sure it's clean, purging gas through the pilot hole of the gas valve and disconnecting the gas valve and reattaching at the union lets me "reset" the gas valve.

Gas valves area very sensitive to pressure change.

 

Is your pilot a stable blue flame or does it have a yellow tip ?
If it nice and blue, is the flame surrounding the top 1/3 or so of the tip of thermocouple ?
If it’s yellow tips, the pilot itself will need cleaning.
LP gas or Natural?