Inch of water
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Inches of water, "wc, inch water colum (inch WC), inAq, "Aq, or inH2O is a non-SI unit for pressure. It is used for measuring small pressure differences across an orifice, or in a pipeline or shaft.[1]
It is defined as the pressure exerted by a column of water of 1 inch in height at defined conditions for example 39 °F (4 °C) at the standard acceleration of gravity; 1 inAq is approximately equal to 250 pascals at 0 °C.
Alternative standard conditions in common usage are 60 °F, or 68 °F (20 °C)
Its most common usage is in the measurement of air ("wind") that supplies a pipe organ and is referred simply as inches. Standard wind pressure in the organ is typically around 3 to 4 inches but some high-pressure stops can be on 25 inches or more.
It is also used in natural gas distribution for measuring utilization pressure (U.P. ie. residential point of use) which is typically between 6 and 7 inches WC or 0.25 psi (~7" WC).
1 inAq = .036126 psi, or 27.67936 inAq = 1 psi.
