With the ever growing popularity of Lava Stones being used in Fire Pits, and in particular the larger sizes, I was recently reminded whilst helping a client with an installation problem how important it is to install these large size rocks correctly in your fire pit.
In is a common and understandable misconception that a fire
pit burner works in the same manner as a domestic gas hob burner, but in fact that is not the case.
On an ordinary gas hob burner, the flame burns adjacent to where the gas exits the burner as is clearly shown in the image on the right.
However, a fire pit burner does not function this way.
In fact it is probably incorrect to refer to this item as a burner. A Gas Delivery System might be more accurate, because it is designed to deliver the gas, but the gas then percolates upwards through the fire glass / lava rock and it should not ignite until it more or less reaches the surface.
The important point here is that the flame does not burn adjacent to the burner, but rather a couple of inches directly above it.
The burner is in fact isolated from the flame by the fire glass / lava rock, as is well illustrated by the picture on the below. In fact the ‘burner’ is actually protected from the heat of the flame by the fire glass / lava rock, as illustrated in the picture below.
So How does this relate to Large Lava Stones and similar Fire Pit Media.
If you were to just insert large size stones into your fire pit, you would inevitably create cavities in, around and on top of the burner.
When you turn on the gas and light your fire pit these cavities would fill with gas and ignite, which in itself is not a good thing. But these cavities may be much closer or even in contact with the burner, and thus when the gas is ignited you would have a hot spot, and the burner is not protected by a layer of fire media as it should be.
Depending on how your stones sit, you may not even be aware that these hot spots exist!
In these circumstances, the very best that may happen, is that you burner will warp due to the excessive heat, and it may even burn holes into the burner, if the hot spot is close or in contact with it, rendering your burner unfit for purpose.
It is easy to avoid this situation once you are aware of it, and can possibly save you some money as well. No down side at all.
The simple solution is to create a ‘filler’ layer of small media around and above the burner, to ensure that no gaps or cavities are created. Then you can place your favorite Lava Stones on top of the filler as required. See the diagram below.
This theory applies to all fire pit media. You must ensure that the burner is covered with an even layer of small size, about 1/4 inch material, up to above the top of the burner.
Do remember though not to cover any spark ignition probes that may have installed in your fire pit tray