One of the most common questions we get from clients is concerning the flame height of their gas fire pit. The two variations of this question are;
- "how do I ensure I get a good flame height" or,
- "why is my flame height so puny".
I always prefer question 1, because it usually, but not always means that the client is at the planning stage, and has not bought any equipment yet, and this is good news. If you are in the position of asking question 2, read on, because a lot of what is relevant in the planing stage will answer your questions too.
Nine out of ten times poor flame height is directly related to the gas supply, as you will see:
Expectations - What is a reasonable flame height?
We would expect a minimum flame height of 6” at the centre of your fire pit. Anything less we would consider unacceptable.
Planning a gas fire pit.
- Your first decision will probably be where in your backyard are you going to locate your gas pit. This article is not about safety, so I will assume you have taken all the appropriate considerations into account, when deciding where you locate your fire pit. If you need more information on this matter here is a very comprehensive article on fire pit safety However, the location, as you will see is highly relevant to the potential flame height you will be able to achieve.
- Your second decision will be about the size, shape and design of your fire pit, which leads on to the size of the burner you will be installing.
It is important to leave at least 3-4” from the edge of your chosen burner size to the inner edge of your fire pit, so that the structure doesn't scorch or even crack from the heat of the burner. So if you decide you want your fire pit inner dimension to be say 30” square or round, you will use a burner of no more than 24” in diameter, leaving 3” clear round the burner.
Why is this important to my flame height?
Now you will see all the variables concerned start to come together.
All burners come with a BTU rating ( British Thermal Unit ), which for our purposes, tells us how much gas your burner is going to consume, to provide a reasonable flame height and heat. Having decided in our example that we would want a 24” diameter burner, we can now check its BTU Rating. At the MagicOfFire.com the 24” diameter burner we sell has a rating of 296,000 BTU. This rating will indicate to a Qualified Licensed Gas Technician what gas pressure will be required, at the gas burner ( not at the gas source ) to allow the burner to operate at its optimum.
But before the Gas Technician can make the final calculation he has to take into account the distance from the gas source to the burner.
Just like a garden water hose, the further the end of the hose is from the tap, the less the water pressure water at the end of the hose. Too far away and the water will just dribble out. Which when we relate back to our gas example, means a very small and weak flame.
We can increase the diameter of the hose, but ultimately it all boils down to the original gas pressure at the source, and the distance it has to travel. Also other factors such as the number of elbows in the gas line may inhibit the gas flow and reduce final pressure for example. This is why it is important to know exactly where you will be building your fire pit.
The reality at this point is that you may not have enough gas pressure at source to provide sufficient gas at your fire pit for the burner you have chosen.
What are your Options.
If you don’t have enough pressure for the burner of your choice, there are some things you can try:
Some people have resorted to installing a larger burner to try to increase the flame height. If our explanation above has made sense, you will see immediately that this will in fact reduce the flame height even more, as a larger burner will have a higher BTU rating and therefore demand even more gas.
It stands to reason then that you could consider a smaller burner, with a lower BTU rating and see if your Gas pressure at source would be sufficient. Alternatively or possible in conduction with reducing the size of burner, if practicable, could you move the fire pit to a location that is closer to the Gas source.
I am presuming at this point that you are working on the basis of tapping into the domestic gas system at a point nearest to the fire pit location. However, another option to discuss with your Gas Technician, may be to access the gas from the Gas Meter and run directly to the fire pit ( You must use a qualified Gas Technician to do this ), which may provide better pressure as the gas flow has not been diminished by other household gas appliances.
You can also apply to your Gas supplier to have your supply upgraded.
As you will have already seen, generally this is quite a complex process requiring specialist tools to measure gas pressures and experience in gas installations. Unless you are a qualified Gas Technician, we really do recommend you hire one and examine all the variables with him/her, prior to purchasing any equipment to ensure that you get the desired result from your fire pit.
Hopefully, the explanation above will enable to have a more knowledgable conversation with your Gas Technician and enable you to reach a viable solution.
Another solution is to use bottled liquid propane gas, which is an excellent fuel for your fire pit, but it does also require a little bit of planning in relation to the burner you select, or more accurately the propane bottle size you will use, is dictated by the BTU rating of your burner. See Chart below.
Consumer Propane Cylinder Dimensions
The dimensions presented above are approximate measurements of common size propane cylinders found in service today. The measurements are not exact so contact your propane company or container manufacturer for precise cylinder dimensions.
Information above provided by Courtesy Of Propane 101
What if I have an existing fire pit?
If you already have a gas fire pit and are not happy with the flame height, my first question to you would be ‘have you ever had a reasonable flame height from the existing installation’. If your answer is yes, then maybe the system just needs a little maintenance.
Remove the fire glass / lava rocks and have a look at the burner. If any of the gas holes appear to clogged with debris, use a small pin or unbent paper clip to clean out the holes. Do not under any circumstances attempt to enlarge the gas holes.
Use compressed air to clean out the gas pipes and ensure there are no blockages. Put everything back in place and light her up.
If there is no improvement in flame height, then please read the preceding part of this article and see if that may bring any issue to mind about the construction of you fire pit and how you could improve upon its gas supply.
As you can see, it really does make a lot of sense to confer with a Gas Technician, before you purchase any equipment. That should avoid any disappointment. Choosing the size of burner ( BTU rating ) knowing that you have the required pressure to fuel it will ensure you get good flame height, providing it is installed correctly. Deciding that you want a particular size burner, then finding out you don't have enough gas pressure can be an expensive mistake.