Welcome to our new series of articles, the definitive guide How To Successfully Build A Gas Fire Pit. In Part 1 of the series, we are looking at the planning process and how to avoid the two most common pitfalls.
Over the past 12 months, lockdowns have meant that many people have discovered or rediscovered the joys of ‘home entertainment.’ In particular, people have embraced outdoor home entertainment, which has almost inevitably led to an increased interest in fire pits.
Traditionally, there is a significant upturn in the construction of fire pits in springtime, and there are already signs that this year will be bigger than ever.
Building a gas fire pit is not complicated. However, understanding how to get the best out of your gas supply can be a little bit tricky, but essential!
If addressed in the planning stages, just two issues will ensure the rest of your project is plain sailing, and the resulting fire pit will have a great looking flame
In Part 1 of our guide to building a gas fire pit, we will run you through the planning stage and identify the two issues that often result in disappointment with the resulting fire pit.
Your Fire Pit Flame
At the end of the day, your fire pit project is judged by its flame. A beautifully built fire pit with a poorly little one-inch flame does not look very impressive.
So what constitutes a good flame? First and foremost, the flame’s height creates a great impression, and then the density is a close second.
Now, we are not talking about ridiculous 4-foot flames leaping out of your fire pit. We are just looking for a nice solid flame a minimum of six inches tall and usually 10-12 inches.
Follow our guide to utilizing your gas supply correctly, and a good looking flame can be easily achieved.
Bigger Burners Do Not Make Taller Flames!
It is a common error that people who are dissatisfied with their existing flame height install a larger burner to achieve a taller flame. The result is usually a smaller flame!
Bigger burners need more gas, so you won’t get a bigger flame unless you increase the gas supply. You’ll get a smaller one!
Planning Your Fire Pit
You should not be concerned with whether you will build a round, square, or any other fire pit shape at this stage.
First and foremost, our interest is the gas supply.
Unless you have extensive experience with gas appliances, we strongly recommend utilizing the services of a Qualified Gas Technician, even if it is just for this stage of the project. You can locate your nearest Gas Technician on Yelp.
A Qualified Gas Technician will establish how much gas you have available for your fire pit project and what size of hard pipe you need to get the gas to your fire pit location in your backyard. These are the two critical pieces of information you need before you purchase any equipment or commission contractors.
All gas appliances are ‘rated.’ They have a BTU rating that tells us two things about the appliance. The first is how much gas they need to operate optimally. The second is how much heat they produce.
Referring back to our comments on flame height, we know that we need to supply the burner with sufficient gas to get a good flame.
In more technical terms, we must supply the burner with its rated level of BTUs to get the best flame.
For example, a fire pit burner rated at 100,00 BTUs needs to have 100,000 BTUs of gas delivered to it.
Therefore, your Gas Technicians’ first task is to appraise your gas supply and the current demands on it. The Technician will then be able to advise you how much spare capacity within the system can be diverted to a fire pit project.
Your gas supply company may be able to provide this information or send a Technician to make the appraisal. It is worth a call to them first before hiring an independent Gas Technician.
This survey applies equally to gas supplied from a ‘street’ supply or if you have a large gas storage tank on your property.
Let’s say your Technician tells you that there are 150,000 BTU available for your fire pit project.
His next task is to make some calculations and tell you what size feed pipe you will need to get 150,000 BTUs to your fire pits location in your backyard. See the Gas Feed Pipe Size Chart at the end of this article.
For example, if your fire pit is 50 feet from the gas source, and you use 3/4″ dia pipe, you would only get about 98,000 BTUs at the fire pit, not the 150,000 available.
However, a 1″ diameter pipe can deliver 177,000 BTUs over a 50-foot run, which is more than enough for the 150,000 BTUs you have available. This will allow you to use a 150,000 BTU rated burner in your fire pit and get the best flame from it!
If as a result of your Gas Technicians survey, you do not have as much gas available for your project as you would have liked, you may have the option to upgrade your existing gas meter to increase your gas capacity. Check with your gas supplier.
Please note we have oversimplified a rather complex set of calculations that involve many factors to be taken into account and is definitely best left to the experts to avoid disappointment.
The logical progression of the whole process should be:
- Discover how much gas you have available.
- Define Feed Pipe size to deliver gas from source to fire pit
- Select a burner with a BTU rating that matches the amount of gas deliverable to the fire pit ( see 1 & 2 )
- Design fire pit structure around selected burner size ( details on this in part 2 of the series )
Following the logical progression will ensure you avoid the common pitfalls usually associated with fire pit construction and low flames.
Not doing so could result in a lot of disappointment and unnecessary expense.
The following is a classic example of what can happen if you don’t follow the logical progression.
We received a call from a gentleman building a fire pit. He was making an ‘L’ shaped design and had selected two very expensive linear burners to install into each leg of the ‘L’ It all sounded like a great project.
The reason he called was that he had just read our article about Hard Piping and getting gas from its source to the fire pit location. Based on our article, he believed his plumber had installed the wrong size of hard pipe.
He was right, but that was the least of his problems!
We asked him, ‘what was the total BTUs of the two burners,’ he said one was 250,000 and the other 300,000 so totaling 550,000 BTU.
His plumber had installed a one-inch diameter feed pipe for the 20 foot run to the fire pit. Our chart showed him a one-inch line would only deliver about 280,000 BTUs, a long way short of the 550,000 required for the two burners. What he needed was an inch and a quarter pipe that would deliver about 570,000 BTU to the fire pit.
With that issue clarified, I just had to ask the big question. ‘If you don’t mind me asking, what is your gas source’?
It turned out he had a domestic residential supply coming from the ‘street’ into his property with a meter. I was hoping he had a large gas storage tank on his property.
I asked if he knew how many BTUs the residential gas supply was sending to his property, he said he didn’t know.
Before he did any further work, my advice was to contact his gas company and find out how much gas he was getting.
As I suspected, his supply was way less than 550,000 BTUs. He did not have enough gas to supply those two big burners, let alone the fact that his domestic water heater and oven, etc., might need some gas too!
There was a happy ending, though. The client had not purchased the two burners at over $1000 each, and when we revised the design, the installed one-inch feed pipe turned out to be just the right size!
Disaster averted, but it was a close call.
Natural Gas, Propane and Propane 20 lb Gas Bottles
The process highlighted in the logical procession applies equally to Natural Gas and Propane installations and to either gas piped into your property via a meter or a large private storage tank on your property.
The only exception is if you have opted to use a 20 lb Propane Gas Tank as your fuel source. A 20 lb tank of Propane holds about 450,000 BTUs.
Modern standard propane gas regulators control the gas tank’s flow and limit it to about 100,000 BTUs per hour.
Therefore, when attached to a 100,000 BTU rated burner, a 20 lb Gas Tank will last about 4 1/2 hours on full throttle.
Because of the regulator’s flow restriction, it is best not to use a burner rated above 100,000 BTU.
- Find out how much gas you have available ( use a Certified Gas Technician )
- Calculate the size of the Gas Hard Feed Pipe ( use a Certified Gas Technician )
- Select a burner based on 1 & 2
- Design your fire pit around your selected burner.
Build A Gas Fire Pit Part 2 – The Structure
In Part 2 of this series, we will look at the fire pit structure that holds your pan/burner. What features it needs, where you can build it, and everything else you need to know.
Gas Feed Pipe Size Chart
For Nat. Gas and Propane Feed Pipe length must include additional length for all fittings. Add approximately 5 feet of pipe per fitting.
For Natural Gas only:
Natural Gas (NG) flow is given in thousands of BTU/hr. One cubic foot of NG gas – 1000 BTU. Nominal pressure at the burner for Natural Gas is 3.5” of water column. (Typical machine supply 5” – 7”).
Natural Gas Example: A machine with a burner that requires 440,000 BTU would need a 1 – 1/4” pipe for a 20’ long run.
For Propane only:
Liquid Propane (LP) flow is given in thousands of BTU/hr. One cubic foot of NG gas – 2516 BTU. This chart refers to low pressure LP, after regulation, standard nominal pressure at the burner for Liquid Propane Gas is 11” of water column.
Liquid Propane Example: A machine with a burner that requires 440,000 BTU would need a 1” pipe for a 20’ long run.