In Reply to: LP questions posted by Walt/Tx on November 22, 2017 at 14:51:42:
Butane and Propane although similar have different properties. 1 gallon of Butane has 102600 BTUs, 1 gallon of Propane contains 91500 BTUs. The boiling point of Propane is -44 degrees. Butane boiling point is +32 degrees. This means that at temps below -44°, propane will not vaporize, and remain in a liquid state. The same for Butane at +32°. Butane tanks are normally buried underground below the frost line to insure vaporization at temps approaching freezing. Butane use was more common in the southern states due to more temperate climate, and rarely, if used at all in the Northern areas of the country. Butanes container (tank) pressure is much lower than Propane. Lighters use Butane due to its lower pressure. As far as pumps are concerned to transfer the products, both with gravity feed from one container to the other, provided the container being filled is Lower than the other. Pumps just make it faster. The Bleeder Screw or vent valve as some term it, is to indicate that the container is at its 80% Full level and to prevent overfilling. It really doesn't function as a pressure relief to decrease filling time. FWIW, SoS.