Adjusting the pilot light flame on a gas fireplace
Most gas fireplaces have a small screw or dial on the control valve that lets you make the pilot flame larger or smaller. The adjustment is usually marked with a minus sign (to lower the flame) and a plus sign (to raise it), or it may be a straightforward screw you turn with a flathead screwdriver. You turn it counterclockwise to decrease the flame size and clockwise to increase it. The whole job takes about five minutes and requires no tools beyond what came with your fireplace or a basic screwdriver.
The pilot light should be a steady blue flame about one to one-and-a-half inches tall. If it is too small, the thermocouple (a safety sensor) may not stay hot enough to keep the gas valve open, and your fireplace will shut off on its own. If it is too large, it wastes gas and can damage the thermocouple over time. Getting it to the right size is a straightforward visual check.
Key Takeaways
- The pilot adjustment is a screw or dial on the control valve, usually marked with plus and minus signs or a slot for a flathead screwdriver.
- Turn counterclockwise to make the flame smaller and clockwise to make it larger, adjusting in small quarter-turn increments.
- The correct pilot flame is steady, blue, and about one to one-and-a-half inches tall, with the tip touching or nearly touching the thermocouple.
- Wait at least one minute between adjustments so the flame can stabilize before you judge whether it needs more change.
- If the pilot will not stay lit after adjustment or the flame is yellow or orange instead of blue, the fireplace may need professional service.
Locating the pilot adjustment on your control valve
The control valve sits at the base of your fireplace, usually behind the front panel or inside the firebox itself. It is a brass or metal box with knobs or dials on it—one for the main burner and one for the pilot. The pilot adjustment is almost always the smaller of the two controls. Look for a screw slot or a dial with a minus sign on one side and a plus sign on the other.
If you cannot find it, check your fireplace manual—the model number is usually on a sticker inside the firebox or on the back of the unit. Manuals often include a diagram showing exactly where the adjustment screw is and which direction to turn it. If you no longer have the manual, search online for your fireplace brand and model number plus "pilot adjustment" to find a PDF or video.
Making the adjustment in small steps
Light the pilot and let it burn for at least one minute so it reaches its normal size. Then look at the flame. If it is too small (less than three-quarters of an inch), turn the adjustment screw or dial clockwise one quarter turn. If it is too large (more than two inches), turn it counterclockwise one quarter turn. Wait another minute and check again.
Make only small adjustments—quarter turns or smaller—because the flame responds quickly and overshooting is straightforward. After each adjustment, watch the flame for at least 60 seconds to let it settle. The flame should be steady and not flicker or dance. Once it reaches the right height and stays there, you are done. Do not adjust it more than you need to, because constant small changes can wear out the valve.
Checking that the flame is the right color and position
A healthy pilot flame is blue with a small yellow or orange tip. If the entire flame is yellow or orange, the burner may be dirty or the gas mixture may be off, and the fireplace should be serviced by a professional. A blue flame means the gas is burning cleanly.
The flame tip should touch or nearly touch the thermocouple—the small metal rod sticking up near the pilot burner. The thermocouple needs to be heated by the flame to sense that the pilot is lit and keep the main gas valve open. If the flame is too far away from the thermocouple, the fireplace will shut off even though the pilot is burning. If you adjusted the flame and it still does not reach the thermocouple, the thermocouple may be bent or out of position, and you may need a technician to reposition it.
What to do if the pilot will not stay lit after adjustment
If you adjusted the flame and the pilot still goes out on its own, the problem is usually that the flame is still too small to heat the thermocouple. Try turning the adjustment clockwise another quarter turn and wait one minute. If the pilot stays lit, you have found the right setting.
If the pilot still shuts off even after you have made the flame as large as the adjustment allows, the thermocouple itself may be failing or the control valve may be faulty. These parts cannot be adjusted further and will need to be replaced by a professional. Do not keep trying to adjust the screw past its normal range, because you can damage the valve.
Common mistakes to avoid when adjusting
The biggest mistake is adjusting too much at once. A quarter turn is usually enough. If you turn the screw a full rotation or more, you may overshoot and then have to turn it back, wasting time and potentially wearing out the valve. Another common error is not waiting long enough between adjustments. The flame needs at least one minute to reach its steady state, so if you adjust it and when ready adjust it again, you are working with incomplete information.
Do not confuse the pilot adjustment with the main burner control. The main burner knob is usually larger and controls the size of the flames you see when the fireplace is running. Turning that knob will not fix a pilot light problem. Also, do not force the adjustment screw. If it feels stuck or very hard to turn, stop—forcing it can strip the threads or break the valve. A stuck screw usually means the valve needs professional cleaning or replacement.
When to call a professional instead
If the pilot flame is yellow or orange instead of blue, even after you have cleaned the burner area, the fireplace needs professional service. A discolored flame usually means incomplete combustion, which can produce carbon monoxide. Do not continue using the fireplace until a technician has checked it.
If the pilot will not light at all, or if it lights but goes out when ready no matter how large you make the flame, the problem is beyond adjustment. The thermocouple, the control valve, or the ignition system may be faulty. These repairs require specialized tools and knowledge. A gas fireplace technician can diagnose the problem in one visit and replace the part if needed. Do not attempt to take apart the control valve yourself.
Frequently Asked Questions
Which direction do I turn the screw to make the pilot flame bigger?
Turn the adjustment screw clockwise (to the right) to increase the flame size. Turn it counterclockwise (to the left) to decrease it. If your fireplace has a dial with plus and minus signs instead of a screw, turn toward the plus sign to increase the flame and toward the minus sign to decrease it.
How tall should the pilot flame be?
The pilot flame should be about one to one-and-a-half inches tall. The tip should touch or nearly touch the thermocouple rod. If the flame is less than three-quarters of an inch, it is too small and may not keep the gas valve open. If it is taller than two inches, it is wasting gas and can overheat the thermocouple.
Why does my pilot light keep going out after I adjusted it?
The flame is probably still too small to heat the thermocouple enough to keep the gas valve open. Try turning the adjustment screw clockwise another quarter turn and wait one minute to see if the pilot stays lit. If it still goes out even after you have made the flame as large as possible, the thermocouple or control valve may need to be replaced by a professional.
Is it safe to adjust the pilot light myself?
Yes, adjusting the pilot flame size is a safe, routine maintenance task. You are only turning a small screw or dial—you are not taking apart the fireplace or working with the main gas line. However, if the flame is yellow or orange instead of blue, or if you smell gas, stop and call a professional before using the fireplace again.
What if I cannot find the pilot adjustment on my fireplace?
Check your fireplace manual for a diagram showing the control valve and adjustment location. If you do not have the manual, search online for your fireplace brand and model number plus "pilot adjustment." You can also contact the manufacturer directly with your model number, and they can tell you where the adjustment is or send you a manual.