Pressure turns stored liquid into usable fuel
An RV propane tank works because pressure keeps much of the fuel in liquid form, where it occupies far less space than the same amount of propane as a gas. Inside the tank, liquid and vapor sit together: some propane evaporates above the liquid, creating pressure that pushes vapor toward the heater when a valve opens.
As propane leaves, more liquid evaporates to replace it. That change from liquid to gas draws heat from the surroundings, so a tank can feel colder while fuel is being used. The pressure regulator reduces the tank’s variable pressure to a lower, controlled supply suitable for the appliance.
A small burner heats a separate water supply
At the heater, propane mixes with air and burns in a combustion chamber. The flame heats a metal passage or heat exchanger; water flowing through it absorbs that heat without mixing with the flame or exhaust. A thermostat and burner controls stop the heating once the water reaches its set temperature, then restart it as needed.
This arrangement lets an RV carry a compact fuel supply and heat water without relying on a large electric connection. The tradeoff is that propane use depends on conditions that affect evaporation—especially cold weather and high demand. In chilly surroundings, the tank may vaporize fuel more slowly, so the heater can struggle to maintain its usual output. The hot shower begins with liquid packed under pressure, but the flame itself is fed by gas.
