There are always concerns about losing the propane supply when the temperatures get well below freezing. Hopefully these notes will help understand the situation a bit better in the cases of a closed propane tank feeding appliances such as a furnace, a water heater, a generator, or a BBQ.
It is pretty cold, and some folk may experience`issues with their appliances operating properly. However, if one has a decent sized tank and properly sized lines and a tank that is properly filled (not too much, not too little) then at temperature lows forecasted for Apsley for this week (Jan 23, 2026), all should be well. Please note that wind chill is not a consideration here, just the actual temperature of the propane.
- Propane has a boiling point of -42degC, meaning that if liquid propane is warmer than this, it will evaporate and enter its gaseous phase. Similarly, any propane vapour that gets cooled below this temperature will condense.
The liquid resides in the bottom of the tank and the propane vapour resides above the liquid.
In a closed tank at a given temperature (warmer than -42degC) the gas and liquid remain in equilibrium, meaning that as many molecules of liquid convert to gas as gas molecules convert to liquid, and the pressure stays constant. This pressure is a function of the temperature.
- when the temperature is warm enough to allow a vapour phase to exist, then the pressure in a closed propane tank is strictly a function of temperature, no matter the actual amount of propane in the tank. (assuming tank is not completely empty or completely full). The higher the temperature, the higher the tank pressure.
- Propane tanks should never be completely filled and should never be low on liquid. There needs to be a decent reservoir of gas in the tank above the liquid. As gas is drawn off it briefly reduces the tank pressure which basically increases the vaporization of the liquid, moving the system back towards the equilibrium pressure.
- Pressure regulation is critical for safe operation. In a typical cottage setting there is a regulator right at the tank limiting the pressure going to the supply line. There is usually also a lower pressure regulator at the appliance to insure proper operation.
As the temperature decreases two important things happen.
- The tank pressure drops. This is inconsequential so long as there is sufficient pressure to feed the appliance(s) as determined by the device’s regulator.
- The rate of conversion of liquid to gas in the tank also drops. If this rate is less than the rate of consumption, then internal tank pressure will also drop potentially leading to delivery problems. (if this is happening to the point of no flow, after a bit, with the appliance off, the pressure will rebuild)
Things to minimize cold weather propane problems.
- Have sufficient space in the tank above the liquid for the propane gas to occupy. Do this by having a large tank, and also by not having the tank too full. If the tank is a horizontal one, then a half-full tank also maximizes the gas/liquid interface area which aids in the rate of vaporization. (meaning that hopefully the liquid evaporates at a faster rate than the gas is being consumed when it is extremely cold)
- If possible, get your supplier to install a tank sensor that you can monitor remotely. He likely does a good job of monitoring your levels, but it is nice to be able to check the situation yourself. Typically, you want to fill to 80% and get a refill at 30%.
- Have adequately sized delivery lines, especially if more than one appliance is requiring gas at the same time.
Chandos Lake Science 2 