Inches of water column is a unit of pressure mainly used in North America to measure small differences in pressure. 1 inch of water is the pressure exerted by a 1 inch high column of water at a given temperature. It can also be represented as in WC, inAq, inches water gauge, or in H2O. Air and other industrial gasses are often measured in inches of water when at low pressure rather than inches of mercury or pounds per square inch (psi).
