Home & Garden Columns

About the House: Can You Light Your Water Heater?

By Matt Cantor
Wednesday March 25, 2009 - 06:19:00 PM

In some sort of way, the society is divided up into two groups. Those that can fix things and those that have to negotiate with the first group to get the fixing done. If you’re tired of wheedling with false compliments, baking cookies and standing there while forcing an adoring expression as Harold lights the water heater after the gas has gone out, I’m here to help (and I can’t see you, so you can stick your tongue out and make a face and finish by burning this paper). 

This really is something everyone needs to know how to do, and while diagrams are quite helpful in such cases, we won’t need them because this is really fairly simple. By the way, a lot of people don’t know how to light their water heater. 

Your water heater has a control box on the front of it. Now get down on the floor, bring a flashlight and take a close look. If you are actually going to light the water heater (you could do this if you’re feeling adventurous) bring a “wand-style” lighter—one of these lighters that has a trigger and a nose that is several inches long. These enable you to put the flame deep inside something without putting your hand all the way in there. For this job, it’s almost a must. If you don’t have this, you’ll either need very small hands and a match or regular lighter OR some long matches that cost a lot of money. I really like the wand lighters. I would suggest that you get one and keep it near the water heater (tape it to the wall nearby). 

Take a look at the controller on the front of the water heater. It has a large dial that lets you set the temperature of the water. Interestingly, water heaters don’t know how hot their water is, so you can’t set a specific temperature. There are too many variables to allow them to do this, so they just offer a relative scale from Vacation (not heating at all) to low to hot to hotter. If the water is too hot or too cold, you just turn the knob a little in the direction you want and test the water in an hour to see if you’re happy with the new setting. It may take a few days to get it where you want it. And be careful: scalding is not uncommon. 

The control box with the big dial (the thermostat) also has a dial (usually on top) that says On, Pilot and Off, as you turn the dial to various settings. Find the mark that lines up with the selection. This will be lined up with the On setting when you approach a working water heater. If you turn the dial to the Pilot position, you will note that you can then depress an adjacent button that was blocked in the On or Off position. That’s the pilot override button. Sometimes, the whole On, Pilot, Off button depresses when it’s in the Pilot position. You’ll have to look and explore. Don’t be afraid. Some very dumb folks have mastered this (Harold, for instance) and you’re pretty smart.  

The point of finding and pushing this part down is that this is the secret to relighting the water heater. 

When the water heater pilot goes out (let’s say the gas gets turned off for a short while) it is designed to shut itself off and prevent more gas from coming out. This keeps your house from blowing up (good idea, right?). So, in order to relight the pilot light (a little flame that is always on so that when the burner comes on, it will immediately begin to burn and not allow for a gas build-up and potential explosion), we have to “override” the feature that turns the gas off when the pilot goes out. That’s what the button is for. But, you may ask, what keeps the gas on when I let go of the button? The answer is electricity from an amazing little device called a “thermocouple.” 

If you will look inside the burner compartment of your water heater (you need to get down on the floor in some cases because it’s right at the bottom of your water heater) you will find three things. A large disk-shaped burner with a large shiny metal tube that feeds to it from the control box and two small devices that are mounted on a metal clip on your side of the burner. These two parts are the pilot jet (nothing more than a small gas tub ending with a shaped piece of metal where the pilot gas will burn) and the thermocouple. The thermocouple (they also used to be called co-generators) is a little probe that is placed right in the path of the pilot flame and when it is heated, it sends a tiny current back via a wire (look for the wire, it’s right next to the small gas tube for the pilot light) to the control box.  

So now we know all the players. Here’s the play. If the pilot has gone out, you will open the door or doors that cover the burner compartment at the bottom of the water heater (smell and be sure that there isn’t gas coming out just as you would with your stove). Keep your face away from the working area. 

Turn the dial to Pilot. Push the button or dial down and you should be able to hear at little bit of gas coming out of the pilot jet. Light it with your lighter right away and keep the button pushed down. You will need to keep the button pushed down for at least half a minute. If you release the button after 30 seconds and the pilot goes out, your thermocouple may be getting old and run down (like me) and may need to be heated for a longer period. Try a full minute. I’ve found cases where it took three minutes or more. If it’s getting to be longer than that, the generating capacity of your thermocouple may be shot and you may need to replace it (time for a plumber). 

What’s happening when you hold the button down is that you are warming the thermocouple, which, in turn, sends a tiny current to the controller, saying that gas should be allowed to flow. When you let off the button, the flame keeps the thermocouple talking and we’re in business. The thermocouple is also telling the controller that when the water gets cold, it’s OK to open the big valve and allow the burner to come one (because it knows that the pilot is going and that it will light the gas right away when it comes on). 

When you’re done, close the door or doors to the burner compartment and open the champagne. You’re amazing.  

Now, some exceptions and other cool things. There are modern water heaters that are sealed off at the bottom and do not let you get inside with your lighter. Not to worry, they have little sparkers that reside inside the compartment right next to the burner. There are “piezo-electric” and use a quartz crystal to generate a spark when you push a button that is right next to the control-box. These are small buttons and you have to look for them but they are readily discernible once you’ve spotted them. When you push the button, you’ll hear them click inside the combustion chamber. By the way, these sealed “FVIR” water heaters are safer in your garage where gasoline fumes may accrue at floor level. 

The last thing (and this is like a present because you’re so amazing) is that you now know how to light many other gas devices that also use a “pilot-safety” device (something that uses a thermocouple to be sure that the pilot is actually lit). Your old furnace may have exactly the same configuration and a very similar control box with the burner simply having a different shape (not a disk shape). Many floor furnaces have a pilot safety device on them (or added as an upgrade). Wall furnaces are most the same as this too. 

Go look at all your gas devices. Crawl underneath, get down on the floor, move the old boxes away and see what you now can do. Are you cool or what!? 




Got a question about home repairs and inspections? Send them to Matt Cantor at mgcantor@pacbell.net.