pound force per square inch
Pound force per square inch (psi) is a unit from the Imperial system defined as the pressure resulting from a force of one pound-force applied to an area of one square inch. It is used in various applications such as tire pressure and hydraulic systems.
mm of water
The millimeter of water (mmH₂O) is a unit of pressure exerted by a 1 millimeter column of water at 4 degrees Celsius under standard gravity.