Fire pit burners come in many different shapes and sizes, and two different groups:
Standard burners - gas escapes through holes in the burner tubes. These are mass produced units and are perfectly suitable for the most domestic and commercial fire pits.
Non-Standard - Gas is forced out of nozzles. These burners are handcrafted with a price point to match. They can produce spectacular flames and surprisingly use less gas than the standard burners.
This article only refers to Standard Type Burners.
Standard Burner Non-Standard Burner Type
How Does A Gas Fire Pit Burner Work
We all know what the gas burner on a grill looks like, so it's logical enough to think that's how a fire pit burner works, but that is not the case. Unfortunately, many fire pits that you see are not set up correctly.
The Standard types of burner should be buried under a minimum of a 1 - 1/4 inches of fire glass or small sized lava rock ( 1/4 to 1/2 inch ). Under no circumstances should you be able to see the burner!
The gas percolates up through the fire glass/lava rock and only ignites as it escapes out of the top, so at least 1-1/4 inches above the burner, not next to it like the gas hob burner.
The gas finds its own way up through the fire pit media creating a larger more natural looking random flame footprint.
If the gas ignites right next to the burner it will create hot spots and warping and will ultimately damage the burner and need replacing. It could even burn holes in the burner and that would become dangerous.
What size burner should I Choose?
Selecting the correct size burner is the most important part of your project. All burners are given a Btu rating, and this tells us how much heat they generate and how much gas they use.
- A typical propane patio heater generates about 45,000 Btu's of heat.
- A 6" diameter fire pit burner is rated at 80,000 Btu's
- A 12" diameter burner is rated at 92,000 Btu's. ( based on American Fireglass burners ).
To get the best flame from any sized burner you need to match the Btu rating of the burner to the available Btu's you have from your gas source.
Using A 20 lb Propane Gas Bottle
If you have decided to use a 20 lb propane gas bottle ( contains 430,000 Btu's ) and you select a 12" diameter 92,000 Btu rated burner, then you will get about 4 1/2 hours of burn on 'full throttle ' per bottle. ( 430,000 divided by 92,000 ).
If you choose a 6" 80,000 Btu rated burner and ran that at about 2/3's throttle ( roughly 50,000 Btu ) you would get about 8 hrs burn time, and generate about a 12-inch tall flame.
At the other extreme connect a 36 inch, 440,000 Btu burner to the same gas bottle, which you would never do because you probably would not even get a flame, but that would, in theory, empty the gas bottle in less than an hour!
Using Your Domestic Gas Supply
Tapping into your domestic mains gas supply is more complicated. We strongly recommend using the services of a qualified gas technician to get this bit right. You domestic supply is calculated on providing enough gas for the appliances in your house. Hopefully, there may be some spare capacity.
Once you gas technician has advised you of the level of Btu's you have available, then you can select the matching sized burner. He will also advise you on the diameter of the gas line required from the gas source to the fire pit. The further the gas has to travel the larger diameter pipe will be required. You can see a table for both natural gas and propane calculations here.
The takeaway here is not to fall into the trap of thinking bigger burners equal bigger flames. If you don't have sufficient gas supply bigger burners mean smaller or even no flames. Match the burners Btu rating to the Btu's you have available and you won't go wrong.
For an outdoor fire pit we always recommend using Stainless Steel burners, they are very durable when set up correctly and usually have a 5-year warranty. Black steel burners are cheaper but outdoors will not last as long. Some Non-Standard burners are manufactured from brass and this is probably more durable than Stainless Steel and some have Lifetime Warranties.
When using standard burners with propane they must be fitted with an air mixer valve, unless the manufacturer states otherwise. For indoor propane installations, National Codes/Ordinances require burners to installed in a burner pan. For outdoor living space propane installations using burner pan is sometimes but not always required by the local codes.