The pilot light went out on my gas water heater. I followed the instructions and had it lit three times now for about 15 minutes each time but it wont stay lit. Not sure what to do at this point?

  • 4
    Call a plumber/heating engineer. Seriously.
    – ChrisF
    Commented Jul 28, 2011 at 20:53

6 Answers 6


It could be that the Thermocouple has failed or is failing. This would cause the system to think there is no flame present, and shut off the gas supply for safety (so it doesn't fill the house with gas).

If you don't feel comfortable working on the heater; or you don't have the knowledge and/or tools to do so, call a trained professional to come take a look.

  • That's what I've read but was confused when they said it would light and automatically go out. This is not the case right now. Commented Jul 28, 2011 at 21:14
  • @Crystal: If the thermocouple has completely failed it will go out immediately, but if it is just stating to fail the pilot may stay lit for some time.
    – Tester101
    Commented Jul 28, 2011 at 21:39
  • Oh I see...well I lit it again about 25 minutes ago after moving some stuff in the garage that may have been blocking the bottom vent....lets hope it stays lit. Thank you very much!! Commented Jul 28, 2011 at 21:41
  • @Tester101, just for my personal reference: In the USA is it legal to work with gas in a domestic dwelling without some kind of "gas professional certification"? In the UK it's illegal to do such work unless you're "Corgi Registered", though I see that recently changed slightly, Council for Registered Gas Installers.
    – Mike Perry
    Commented Jul 29, 2011 at 15:55
  • @Crystal: I've had a thermocouple fail in exactly this way - the boiler stayed lit for a few minutes, then went out. Suggest it's time to call a plumber/engineer, a thermocouple shouldn't be too expensive as they fail fairly often. Commented Aug 1, 2011 at 16:10

Several possibilities:

There's a thermal shutoff that automatically stops the gas if the pilot light doesn't heat it up. This prevents you from leaking unburned gas into the home, which would be very bad. Check that the probe is in contact with the pilot flame. The fact that it stays on for 15 minutes makes me think this may not be the issue, but depending on the model, there may be a delay after lighting the pilot before this activates.

The next concern is a lack of ventilation. Make sure fresh air can get to the water heater. Get out the vacuum and cleanup all those cobwebs and flammable dust balls. The location of the water heater should have a fresh air supply, either with a louvered door or a vent line that goes outside. Make sure these are open.

Related to a lack of ventilation is over-ventilation, or a draft that is blowing out the light. Make sure the shields are in place on the heater and that the HVAC doesn't have anything blowing directly on the hot water heater.

The last thing I can think of is a lack of gas coming into the line. This could be from a valve not being all the way open. It could also be from a condensation build up in the line. There should be a small bit of pipe leading to a dead end cap pointed down somewhere after the shutoff. I suppose it's possible for this to fill up, but have never seen it myself. Whether shutting off the gas, opening this up and allowing any moisture to drain is a DIY job, I don't know, maybe someone else will comment.

  • It's hard to see the probe. I only have a small window to look through. The water heater is located in the garage and has a vent through the top of the garage and then two on the side of the garage that all seem clear. Commented Jul 28, 2011 at 21:13
  • @BMitch, just for my personal reference: In the USA is it legal to work with gas in a domestic dwelling without some kind of "gas professional certification"? In the UK it's illegal to do such work unless you're "Corgi Registered", though I see that recently changed slightly, Council for Registered Gas Installers.
    – Mike Perry
    Commented Jul 29, 2011 at 15:55
  • 1
    @Mike: It's my understanding that attaching or removing a device requires a permit and/or certification (not that everyone does that, though they should). Lighting a pilot light and adjusting the location of the thermocouple should be fine as long as you're not disabling a safety feature. Replacing the thermocouple I'm not sure, and opening up the condensation trap, I'm even less sure.
    – BMitch
    Commented Jul 29, 2011 at 16:10
  • @BMitch, thanks! Sounds about the same as the UK.
    – Mike Perry
    Commented Jul 29, 2011 at 16:24
  • We just had the same thing happen. We changed the entire burner system because it is a one piece unit. It would light just fine but kept going out after 30 seconds. Took the above advise for dusting under water heater and is working fine now. Hallelujah. I can take a bath. So check under for dust and dirt from animals if you have any.
    – user23679
    Commented Jul 10, 2014 at 19:13

I currently had this issue with my Whirlpool water heater. It was under warranty so I called and they directed me to hotwater101.com. The problem turned out to be the gas control valve. It required removing the control valve (the front piece where you set temperature light it, etc.) It wasn't too bad to replace, but did take about 2-3 hours. You need to drain the water heater, turn off gas, etc. If it's not under warranty the part ran about $70 at Lowes. Since mine was still under warranty Whirlpool paid for it. So that's something you'll want to check in to. They have a video and pdf on the site on how to replace it. If yours isn't whirlpool I'm not sure how different it will be. Mine has worked great since I replaced it. Hope I have helped.

(I should mention that they thought it was my thermocouple at first, but since it did light and would stay lit for half an hour that rules that out.)

Replacing Gas Valve Video

Replacing Gas Valve PDF

  • Thank you. So far, by moving stuff completely away from the water heater and all vents we continue to have hot water. I did find out that parts are under warranty for another year so I will keep this information for future reference. Commented Jul 29, 2011 at 15:29

The sealed units have a heat link underneath the gas burner. When the vents get clogged by dust and dirt, the combustion chamber overheats and the heat link melts. Beneath the heat link is a spring clip which holds down a metal rod. What you will see when you take out the burner is a loose spring clip because it popped out when the link melted. This heat link simply holds down a metal rod that springs up and cuts off the intake air. Without intake air, your unit may light after a while but will not stay lit and will not relight until a little fresh air leaks in. To replace the link you have to contact the manufacturer who will send you one for free only one time. You need to shove the rod back down and slip the new heat link into the slots on each side which hold it in. You also need to clean the air intakes on both sides of the hot water tank by using a vacuum cleaner and/or compressed air. Then I suggest periodically repeating the cleaning process. I found a three minute video on Youtube that showed this clearly.


The sealed water heaters DO need air circulation. At the bottom of water heater there is a black flitter that goes around the bottom. It needs to be cleaned yearly as well as under the water heater. The flame arrerster under the burner needs to be cleaned also. This is how these unit get air. The arrestor an the area underneath the water heater is the path the air takes. This needs cleaning with shop vac yearly.

If the burner area was completely seal off from getting air, you would never get it to light. Three things are needed to make fire - Ignition source - Fuel - Oxygen You should never remove the glass window or any others parts off the water heater. Carbon monoxide is vented out of the area and altering the air flow can result in carbon monoxide poisoning and death. Carbon monoxide is deadly and odorless.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Commented Jul 11, 2019 at 20:45

I've read everything online about these heaters and the vids on YouTube. My theory isn't that its the thermocouple or just lack of air going in,its that these sealed water heaters don't let air OUT of the pilot light area. Pressure builds up when the burner kicks in with a small blast- blows out the pilot. If you remove that glass window..air can escape...the heater works fine. Just use some wire screen instead of glass to cover and it also keeps the pilot light from getting too large an air intake..so its Goldilocks..just enough air in,and enough going out.

Of course,this is all at your own risk,etc. But,c'mon water heaters worked like that for decades,and nobody complained.

  • The danger here is that your exhaust vent is somehow clogged and you're now venting carbon monoxide directly into your house. Be careful.
    – Shrout1
    Commented Oct 16, 2017 at 3:17

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