Inches of water, inAq, "Aq or inH20 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 distribtuion for measuring utilization pressure (U.P.) which is typically between 6 and 7 inches or .25 psi.

1 inAq = .036126 psi, or 27.67936 inAq = 1 psi.

References

1. Inches of something

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Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Inch of water". Image Credit.

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