does the pressure in a filled propane tank decrease when the valve is opened?
Answer Trey, Yes and No. If you have a guage on the tank that shows the pressure inside the tank, then you will see it go down when the valve is opened. However, once the valve is closed, the pressure will go back up. It all has to do with vapor pressures. Essentially, any time there is a liquid (propane) in a closed container, there will be a portion of the liquid that converts to gas and maintains a constant pressure. Some liquids, like propane, have very high vapor pressures so a lot of the liquid converts to gas and creates a high pressure. Other liquids, like mercury, have low vapor pressures so very little of the liquid is converted to a gas. To make things one step more complicated, temperature also affects the vapor pressure. Colder temperatures lower the vapor pressure and hotter temperatures raise the vapor pressure. So, if the propane tank is kept at the same temperature, it will have the same pressure until there is no more liquid propane in the tank. At that point the pres
