What is the relationship between "inches of water guage" and another more common measure of pressure

Question

I have looked and looked and I have not been able to find a definition of inches of water with respect to a measurement of pressure.

Answer 1

1 in water = 248.8 N/m2= 0.0361 lb/in2 = 25.4 kg/m2 = 0.0739 in mercury = 1.8664 Torr = 2.4884 millibars

Inches W.G. are generally used when working with air handling systems, where pressure differences are normally quite small.

Answer 2

Inches of mercury is the more common measure of absolute pressure (or vacuum), 29"Hg is pretty much a decent vacuum - this simply means that if a very long test tube were submerged in mercury and the closed end were lifted out and raised leaving the open end submerged, the tube could be raised to any height, but the column of mercury would only be 29" high - a measure of the vacuum above it.

"Inches of water" uses the exact same principal, except water is the medium and not mercury. If you were to perform the same experiment with water, you would find the column would be 29 FEET high - or 348 inches.
As you can guess, a scale with 348 divisions is a heck of a lot more precise than one with 29 divisions - especially when measuring small differences in absolute pressure (the difference between the ambient pressure and the pressure being measured.)

Answer 3

Inches Water