Once upon a time, pilot-light problems were usually just a matter of replacing the thermocouple. However, a federal regulation that took effect in 2002 created a new set of pilot-light problems. If your heater is that age or newer, take a look, also, at the Tanklet "FVIR Issues." Pilot Light Problems
Q: I have an A.O. Smith. The pilot is on but when you turn heater on the burn won't fire up....
A: There is a knob on top of the gas control which says, ON, OFF and PILOT. Make sure it is firmly in the ON position. Hopefully it's that easy. -- Larry (1/5/08)
Q: My pilot light won't stay lit at higher thermostat settings. It will stay lit indefinitely (weeks) on low thermostat settings, but when set beyond mid- point, the pilot light will go out after the new higher set point is reached and burner cycles off. I've already changed the thermocouple and cleaned the pilot oriface. Draft and condensate aren't a problem. Some of the similar posts haven't quite touched on or answered my particular problem. I would appreciate suggestions that account for the pilot light differences based on high vs. low thermostat settings. This is a GREAT forum! Thanks!
A: The only thing that comes to mind is to watch the pilot light as the main burner comes on and goes off. I suspect the main burner is pulling the pilot flame away from the thermocouple or going out with a pop, which can blow out the pilot. Let us know what you see. -- Larry (11/9/2007)
Q: OK, this is my second posting. We fixed problem one with the pilot not lighting at all. I disconnected the pilot line and cleaned the pilot head and now we have a pilot lighting. Now on to problem #2. After the heater cycles and heats the water, the burner turns off and the pilot goes out. Is this a bad thermalcouple? What happened was my boiler room flooded with 4" of water 2 weeks ago and then again this past Sunday. After it all dryed, I went to work on the pilot. After disconnecting the gas line from the thermostat, I could hear the gas and was able to tell the pilot line was clogged. I cleaned it, hooked everything back up, did a soap bubble test to make sure everything was sealed properly, and then proceded to light it. It lit with no problem, cycled once and went out. I though maybe the temperture was too high, (it was between Hot and Very hot) I adjusted it and relit the pilot. Again, cycled once and went out. There is no gas smell so no gas leaking from line or pilot. Please help!! It is a Kenmore Power Miser 10 natural gas heater.
A: Did you get to the pilot orifice and clean that? If it's partly blocked, the pilot flame could be too small. This would not heat the thermocouple sufficiently and might be pulled from the thermocouple when the main burner shuts off. Sensing a lack of heat, the control would shut down. It's only a guess though. Watch the flames as the main shuts down and see if it behaves as I've described. If so, the orifice for the pilot may need some TLC. -- Larry (8/4/07)
Q: I picked up your address from your Internet site. Quick question for you. I have a Sears Kenmore water heater about 9-10 years old. The pilot light would not stay lit. I'd light it and it would heat for about 10-20 minutes and go out. I replaced the thermocouple and it did the same thing. I would light it and it would heat for about 20 minutes and go out. I could not relight the pilot light until it cooled down. I played with the position of the thermocouple and it doesn't seem to work. The thermocouple seems to be in the flame. Any suggestions or just buy a new one? Thank you for your time.
A: Check to see if the vent is blocked. Leave the hatch cover off when it fires and watch the flame. There should be no lazy yellow flames. See what happens when it goes out. Look for soot in the combustion chamber and the vent. It's possible also that leaving the hatch open will alter the condition that makes it go out. But these are the sorts of things that might cause the problem you describe. -- Larry (1995-2000)
Q: Tried to relight my gas water heater after about a year of being shut off. (Gas supply off, Temperature to minimum, On/Pilot/Off switch to off, water in tank not drained.) Pilot stays on after thermocouple warms up, approx 45 seconds. Burner never comes on, regardless of temperature setting. Regardless of whether water is drawn from tank or not. Are these gas controls replaceable? How much are they on average? Do I need to get inside the tank to remove the control? There is a removable screw on the bottom. Is it for bleeding the control? Thanks in advance for your help!
A: It sounds like the gas control valve isn't opening when it should. Probably not a warranty issue since you didn't say it was a new heater. Go through the lighting operation again. That is, light pilot, then turn front knob on control to vacation or coldest setting, turn top knob firmly to on position, then turn dial on front up until it clicks on. If you doesn't hear or feel it click on, you could remove the knob and turn the shaft further to see if that does it. The shaft will have to be turned back and knob replaced for safe and correct operation. But, ultimately, if the control doesn't work in the correct range, it must be unscrewed and replaced. They cost roughly $70. The screw on the bottom is a pressure tap. Leave it alone. It is for checking gas pressure. The control just screws in. Replacement involves draining the tank but not squeezing inside! -- Larry (1995-2000)
Q: Hi. I was wondering if you could tell what could be wrong with my water heater. The pilot light does not wanna stay lit, My husband has changed the thermocouple twice now. We have to light it at least three times a day. Do you have any suggestions to my problem? Thank you for your time.
A: Make sure the tip of the thermocouple is in contact with the pilot flame and that both of the hatch covers are in place, (to prevent any breeze from blowing out the pilot). If those don't work, see that the pilot flame is the size it should be. You should likely get help with this one. If the control has been wet, all bets are off and you should replace it. -- Larry (1995-2000)
Q: Greetings! First let me say that I have read ALL relevant information on this site, including all relevant-sounding forum posts going back to the very inception of the board. Based upon these very informative posts (thanks guys), I have a pretty good idea what's wrong. What I'd like to know (and for the benefit of the searhable archive) is what I might be able do about it myself.
In short, the situation is that suddenly in the last couple of days my standing pilot light has refused to stay lit for any length of time. This is not sporadic; I _believe_ it always extinguishes itself sometime after the first cycle, but I have not 100% verified that -- hope to do that sometime today. My first thought was to run out and buy a new thermocouple, but after spending much time reading on this site and doing some troubleshooting, I think that would be fruitless. (See below) There have been no environment nor plumbing changes in my house.
When lighting the pilot it does not always light right away, but then again the selector knob was a bit sticky on this old heater when I went down there so who knows. When I press down on the selector to engage the pilot gas I do NOT hear the gas (even though the pilot does eventually light). During the lighting process it does not always stay lit, but using a match to heat the thermocouple for several seconds usually gets the job done.
I have left the thing alone for 30+ mins while it was recovering and came back and turned the thermostat down to vaction: pilot stayed on fine for the several seconds seconds until I cranked the temp back up and the burner fired up again. (Silly me: Probably should have left it down for a few mins to see if it went out eh?)
The pilot flame is basically on the thermocouple, although it is not totally wrapping around it. The t'couple is not "glowing red" as mentioned in other posts but then again I've never seen one that has. (LOL maybe I'm just used to looking at failing stuff.) The strange thing that I have not seen mentioned is that my thermocouple has a white residue on it, almost scale, right where the pilot flame touches it. I'll post pics here shortly if the forum permissions allow it. I never did quite understand _exactly_ what it should look like when you experts said 1/2" of the end of the thermocouple and "partially" wrapping around it.
I'm assuming gas pressure is pretty much ok because my furnace and gas dryer are working fine. The burner emits a nice blue flame with only an occasional lick of yellow, but then again I don't have an eye for exactly how it's supposed to be normally. There doesn't seem to be any downdraft/heat out of the flue hood or whatever it is called. Venting is nearly straight up through a skinny brick 2 story chimney, lined with small ducting.
The chimney used to be shared by the furnace (2+ years ago) but isn't any longer. I haven't lived in this house for many years, but based on the heater label it was either made in 1983 or 1985 (hey, I'm not complaining at ALL!). But it couldn't have been installed here back then because the whole area was totally underwater during the great flood of '93.
There are still bits of solder on the anode hex nut which tells me the anode has not been replaced since installation. I guess I'm lucky the thing still works at all without any leaks. Good thing my T&P valve is stuck shut so I don't get any water on the floor. (No just kidding!!!! Haven't tested it yet but CERTAINLY will today after seing that pic of the 5 gallon heater explosion in the school).
Anyway, what all of this tells me, as a non-plumber, is that the thermocouple is fine but it's not getting heated properly. The "scale" I mentioned above: Can I just scrape this off with a knife without damaging the thing? That's gonna be my first step I think. Based on other posts I'm getting the feeling that my pilot flame isn't quite what it should be, and even though the residue indicates it's been "about" the same all these years, maybe it has just crossed the line to "not quite enough".
The owners of the site have said two different conflicting things: 1) Clean the orifice out, and in a different post it was said that 2) It takes a carefully trained eye to clean these. I certainly don't have a carefully trained eye, but am going to attempt it anyway if that's what might help. I did read about the guy who "reamed"(??) the orifice out until it yielded a 4" pilot flame -- I will certainly be careful, and don't plan on using any heavy-duty tools. Maybe just a little eyeglass screwdriver to scratch out any obvious obstructions. Anything I should do or watch out for? Will CLR or a similar solvent help without doing any damage? Thanks in advance for those answers!
P.S. On a more frivolous note, would it do ANY good to buy a new anode? This is a State Courier and the hex head is flat so I'm guessing it's aluminum. (Or WAS, before it no doubt totally disintegrated.) I'm rightfully concerned about aluminum but I'm not drinking out of my hot water heater and don't know anyone in their right mind who would, so I guess that's not so much of a concern. But I would like to keep this old beast running as long as possible. Not for economics' sake (I know it will cost me much more), but just to see how long I can keep it alive, on principle. 21-23+ years is pretty good for something that's been totally neglected! Thanks again!
A: Hello: I can't explain the mechanism, but thermocouples do wear out. The right test would involve getting tools that cost a good bit more than a thermocouple. The symptoms do indicate poor output from the thermocouple, so I'd start by replacing it. It has done well to last so long.
Next is to look into the combustion chamber with a flashlight and carefully examine the roof of the chamber (bottom of tank) and bottom of the flue. If you find these dry and without serious rust, go ahead and replace that anode. You'll never get the tank to make it to over fifty years (I've had some good luck with heaters) if the anode isn't changed. When you do that, you might want to remove that plug from the relief valve too (or just install a new valve).
Price a new heater. It will help motivate you to keep this one going! -- Larry
Q1: As I feared, a new thermocouple did not help. The only difference now is I don't have to hold the match on the t'couple to get it to initially heat up -- presumably this is because the new one is more sensitive.
But the heater still goes out even before a complete cycle. I put a video camera on it this last time and even with the full burner on, the whole thing went off after just 5 minutes. Burner & pilot both at the same time. Normally it stays on for 15-20 mins, but this was my second attempt of the day. Always seemed to go off quicker when things were things were still somewhat warm.
I had planned on cleaning out the pilot orifice while replacing the thermocouple but after yanking the whole assembly out I see it is VERY small. Some fine electronics wire is about the only thing I can think of that will possibly fit in the hole. Ooohh just had an idea though... maybe some carb cleaner? With a very thorough rinse and plenty of drying time afterwards?
What made me think this is a pilot problem rather than the t'couple is that the pilot was very difficult to light and stay lit even with the button being held down. And I have to put the match flame right _on_ the opening -- close does not do it here.
Also possibly related: When I put everything back together I did the Windex test as recommended on this site. There is a _very_ slow gas leak near the gas control on the pilot gas tube. Seems the last person to screw around with this heater got a little overzealous with a pair of pliers and squeezed the actual tube a bit instead of just the fitting, causing the fitting not to seal perfectly. Though I will replace it when I can I'm not too worried about this -- been that way for years and it certainly never affected the heater's operation nor caused a detectable amount of ambient gas. I guess unless anyone has any better suggestions my next steps in order are going to be: 1. Clean pilot orifice with carb cleaner and whatever small wire I can find. 2. Replace whole pilot assembly and the gas tube leading to it 3. Assume it's the control and consequently ditch the whole darn heater.
A1: Maybe cleaning the pilot orifice is a good idea, though I'd stick to chemical cleaning rather than a wire. There should be sufficient heat to make the tip of the thermocouple glow dark red. Beyond that, when video-taping, what happened when the pilot went out? Did a drip of condensation hit it? Did the pilot flame float off the burner and go out? Did a breeze get it? Did a furnace connected to the same flue come on? Did the main burner flame push the pilot flame away from the thermocouple?
There must be a cause you can see. Try lighting it and then sitting with it to see exactly what happens. If it goes out, light it again right away to keep the tank heating. See if it will get up to temperature and then stay there. Watch the main burner to see than it is behaving properly. That is, not lifting from the burner, not floating, staying mostly blue... It could be a problem with the vent or supply air rather than with the heater. If it were the main control, it would likely not stay lit at all. The truth is out there. -- Larry (2/17/06)
Q: Hi guys, The manual for my new water heater says I need to install a "dirt leg" (sediment trap) on the gas line going into the heater control box. I did some searches on the Web and can't really find any solid how-to information on doing this. Is there a single part I can go out and buy from a plumbing supply store, or do I have to make a dirt leg out of copper (?) tubing?
Also, the only photos I've seen of a dirt leg show a gas supply line running vertically from the ceiling down to a T connector. The dirt leg continues for several inches vertically below that, while a horizontal line juts out from the T and connects to the heater. However, my gas supply line runs horizontally from the shutoff valve on the wall directly to the heater (it's a corrugated stainless steel line.) Does this make a difference?
If I put a T on this horizontal line so that the CSST supply came in horizontally from the left, the dirt leg extended vertically below, and the heater control was on the right, would that achieve the same effect? Thanks for all your help. This is a great site.
A: To make a dirt leg, put a "T" on a short nipple into the gas control. Use the center port on the "T". Turn the "T" so it faces up and down. On the down side, install a five or six inch long nipple with a cap on the end. On the up side install the gas flex line adaptor. Now gas will make the turn into the control while dropping any debris into the capped pipe. -- Larry (6/20/06)