How to Read an LP Gas Cylinder Gauge: A Simple Guide
Published 20 April 2025
Knowing how to read your LP gas gauge means you can order a refill before you run out. Here is everything you need to know about the different gauge types.
Why Reading Your Gas Gauge Matters
Running out of LP gas mid-cook or during a winter morning shower is frustrating and easily avoidable. Most LP gas cylinders in South African homes have some form of gauge or level indicator, but not everyone knows how to read them correctly. Understanding your gauge helps you plan refills in advance, avoid appliance damage from inconsistent gas flow, and stay safe by knowing when a cylinder is approaching empty.
Types of LP Gas Gauges
1. Pressure Gauge (Dial Gauge)
This round dial gauge screws into the cylinder valve or is built into the regulator. It shows pressure in bar or psi. Important: LP gas cylinders maintain a near-constant pressure as long as liquid gas remains inside, so a pressure gauge reading will stay relatively high until the cylinder is almost empty. A sudden drop in reading signals that you are down to the last portion of gas. Do not rely on pressure alone to estimate remaining gas.
2. Float Gauge (Rotary or Magnetic)
Some cylinders have a magnetic float gauge, a dial or strip on the outside of the cylinder connected to an internal float that rises and falls with the liquid gas level. This is the most intuitive type and functions similarly to a car fuel gauge, with Full, Half, and Empty markings.
3. Transparent Strip Gauge
A strip of heat-sensitive material is attached to the outside of the cylinder. When the cylinder is at room temperature, the liquid gas inside keeps the lower section of the strip cooler. The point where the temperature changes shows the approximate gas level. Run your hand up the cylinder; you should feel a temperature change at the gas level.
4. Weight Method
Every LP gas cylinder has its tare weight (empty weight) stamped on the collar. Weigh your cylinder and subtract the tare weight to get the remaining gas in kilograms. A 9kg cylinder with a tare of 8kg that weighs 12kg total contains about 4kg of gas, roughly half full.
The Hot Water Trick
If your cylinder has no gauge at all, pour a small amount of hot (not boiling) water down the side of the cylinder. The area above the gas level will feel warm; the area below, where liquid gas is present, will feel distinctly cooler due to the gas absorbing heat. The boundary between warm and cool indicates your current gas level. This is a quick, safe, and reliable method used by gas professionals across South Africa.
When to Order a Refill
The best time to order a refill is when your cylinder reaches approximately one quarter full, not when it runs completely empty. This ensures continuous supply and avoids the risk of air or moisture entering the cylinder through an empty valve. If you use gas daily for cooking, we recommend checking your level weekly and keeping a spare cylinder on hand wherever possible.
Frequently Asked Questions
Why does my pressure gauge stay high even when the cylinder feels light?
Pressure gauges measure vapour pressure inside the cylinder, which remains nearly constant until almost all the liquid gas has evaporated. This is why a pressure gauge is not a reliable indicator of remaining gas volume; use weight or a float gauge instead.
My gauge reads empty but the stove still works. Is the gauge broken?
Not necessarily. There is always a small residual amount of gas vapour in a "empty" cylinder that can fuel a stove briefly. Once the flame drops or goes out, the cylinder is truly empty.
Can I install an aftermarket gauge on my existing cylinder?
Yes. Inline gauges that fit between the cylinder valve and the regulator are widely available and easy to install. They provide a continuous visual reading. Always ensure the gauge is rated for LP gas use.
How do I know if my gauge is faulty?
Compare the gauge reading with the weight method. If your gauge reads full but the cylinder weighs significantly less than a full cylinder should, the gauge is likely faulty and should be replaced.