In this month's column, Robert Pelikan covers how to use Boyle's Law to calculate the amount of usable water in a captive air tank.
In this month's column, we'll cover how to use Boyle's Law to calculate the amount of usable water in a captive air tank.
The drawdown capacity of a captive air pressure tank is determined by a formula known as Boyle's Law. Simply put, Boyle's Law says as the volume of the air cushion in a tank decreases, the pressure of that air cushion increases. Conversely, as the volume of the air cushion increases, the pressure of that air decreases. Therefore, for any given tank, drawdown equals the volume of air at cut-in minus the volume of air at cut-out. Stated as a mathematical formula taking the total volume of a pressure tank into consideration, it looks like this: