Pilot Burner Jets Explained: Sizes, LPG vs Natural Gas, and Conversions
What does a pilot burner jet actually do?
It meters the gas. The jet is a tiny, precisely drilled orifice that controls exactly how much gas reaches the pilot flame. That hole size is the entire design of the part — everything else is just a way of holding it in place.
Get the size right and you get a strong, stable blue pilot flame that heats the thermocouple properly. Get it wrong and the flame is either starved or over-gassed, and the appliance becomes unreliable or unsafe.
Why are LPG jets smaller than natural gas jets?
This is the single most important thing to understand about jets, and it catches people out constantly.
LPG carries far more energy per unit of volume than natural gas, and it is delivered at a higher pressure. So to get the same size flame, you need to let less LPG through. That means a physically smaller hole.
You can see it in the sizes we stock:
| Jet size | Gas type |
|---|---|
| Ø0.14mm | LPG |
| Ø0.19mm | LPG |
| Ø0.20mm | LPG |
| Ø0.25mm | NG / LPG |
| Ø0.35mm | Natural gas (also an LPG variant) |
| Ø0.40mm | Natural gas |
The pattern is clear: the LPG jets sit at the small end, the natural gas jets at the large end.
What happens if I fit the wrong jet?
- A natural gas jet on LPG — the hole is too big for the gas. You get a large, roaring, unstable flame, sooting, and potentially dangerous over-gassing. This is the dangerous mistake.
- An LPG jet on natural gas — the hole is too small. The pilot is starved, weak and yellow, it may not heat the thermocouple enough to hold the gas valve open, and the appliance will keep dropping out.
If you have just moved an appliance from a mains-gas site to a bottled-gas site (or vice versa) and it is now behaving badly, the jets are the first thing to check.
How do I convert an appliance between natural gas and LPG?
Conversion is not just the pilot jet. A proper conversion means:
- The main burner injectors changed to the correct size for the new gas.
- The pilot jet changed to match — this is the part most often forgotten, which is why a "converted" appliance still won't hold its pilot.
- The gas pressure / regulator set correctly for the new gas.
- Combustion checked and the appliance certified.
This is not DIY work. In the UK, converting a commercial catering gas appliance must be done by a Gas Safe registered engineer qualified for commercial catering. Fitting the wrong jets is a genuine carbon monoxide risk, not a performance niggle.
What you can do is make sure your engineer has the right parts on the van. Browse pilot burner jets — all sizes, £9.99, UK stock.
How do I find out which jet size I need?
- Read the old jet. The size is usually stamped on it — a number like 25 or 35 corresponds to 0.25mm or 0.35mm.
- Check the appliance data plate. It states the gas type the appliance is set for, and often the injector sizes.
- Check the manufacturer's conversion kit list for the model.
- Never guess, and never drill. Enlarging a jet with a drill destroys the metering and the flame will never be right.
What are the symptoms of a blocked jet?
A blocked jet behaves like an undersized one — because functionally, it is one.
- Weak, short or yellow pilot flame.
- Pilot that lights but will not hold the thermocouple.
- Flame that lifts or flutters.
- Sooting around the pilot burner.
Clean the jet with compressed air, or pass a fine needle through it very carefully. If the orifice is scored, corroded or has been drilled, replace it — at £9.99 it is not worth nursing a damaged one.
Frequently asked questions
Can I just clean the jet instead of replacing it?
Yes, if it is only blocked and the orifice is undamaged. Compressed air first. If you have to force anything through it, you risk enlarging it — at which point replace it.
Are SIT jets interchangeable with other makes?
What matters is the thread and the orifice size, not the badge. We stock SIT and our own jets across the same size range, and they fit the great majority of commercial pilot assemblies.
My appliance was converted to LPG but the pilot keeps dropping out — why?
Very likely the main injectors were changed and the pilot jet was not. The pilot is now running an oversized natural-gas jet on LPG, or a starved flame that cannot hold the thermocouple. Check the pilot jet size.
How fast can I get jets?
UK stock, all sizes £9.99. Order before 10am for next-day delivery, free over £25. Not sure of the size? Call 073 8051 5838 with your appliance make, model and gas type.
Need the right jet?
Shop pilot burner jets · Shop pilot burners · Shop thermocouples · All gas equipment parts
