Gas bottle level indicators: do they actually work?

The short answer

Some do, some only partly. It depends on what the indicator actually measures: temperature, pressure, weight or liquid level.

Temperature strips

They show where the bottle is cooler, which roughly matches the liquid line. They need warm water or a temperature difference to work, and give an approximate reading.

Pressure gauges

LPG pressure depends mainly on temperature, not on how much liquid is left. So a pressure gauge usually reads about the same until the bottle is nearly empty. Pressure also depends on gas composition; it is not a dependable near-empty warning or fuel gauge.

Weighing

Weighing can estimate the mass of gas if you know the tare weight. Before moving a portable bottle, turn off the appliance, close the bottle valve and disconnect according to the supplier’s instructions. Keep it upright, use scales rated for its full weight and subtract the tare in matching units, allowing for accessories not included in the tare. Do not lift a connected bottle or attempt to weigh a heavy installed cylinder yourself.

Ultrasonic level sensors

Sensors such as the WiseTank Bluetooth and WiFi models measure the liquid level from under the bottle and show a percentage in the TANK IOT app, with low and high level alerts. The supplier lists liquid depths of 5 cm to 2 m; this does not prove compatibility with every bottle. The Bluetooth model also has a supplier-listed 5.5 cm blind spot at very low levels.

They need a steel bottle with a flat, clean area in the centre of the base, mounted level. They do not work on aluminium or composite bottles.

Bottom line

For a rough check, follow the thermal strip or cylinder supplier’s instructions; never heat a bottle or use boiling water. A compatible sensor can make checks more convenient if reception works at the installation. Treat readings as planning aids, not guarantees of gas supply. These sensors do not detect leaks.