Explanation of the GasStop gaugeUpdated 2 days ago

The gauge on a GasStop is a pressure gauge. It doesn't measure the exact quantity of propane gas (LPG) in a tank. It is an approximation based on the pressure in the tank at that moment.

On warm days, the gas pressure will rise. A full propane tank may show in the yellow zone (high). This is normal.

On cold days, the gas pressure will decline. A tank may read in the low end of the green zone but still have gas in it.

A tank that reads in the red zone is probably empty or nearly empty. 

If the GasStop will not prime despite pumping it several times, as described in the GasStop instructions, this means the gas pressure in the tank is low. The propane tank should be refilled.