Friction loss is always expressed in which unit?

Friction loss is always expressed in which unit?

• A. psi per foot
• B. kPa per meter
• C. psi per meter
• D. psf per foot

Answer: (A)

Friction loss is the pressure drop that occurs along a length of pipe as water flows. To compare and calculate it consistently, you express this loss as a pressure change per unit length. In sprinkler practice using US customary units, the standard way is pounds per square inch of pressure lost per foot of pipe. This directly matches the typical pipe runs measured in feet and lets you estimate how much pressure will be lost over any length by multiplying the length (in feet) by the rate (psi per foot). Using metric units would give kPa per meter, which isn’t the convention in this context, and psi per meter would mix units in an uncommon way for the usual field calculations. psf per foot isn’t appropriate because psf is a pressure per area, not per length. So the expression that fits the common practice is psi per foot.

Friction loss is the pressure drop that occurs along a length of pipe as water flows. To compare and calculate it consistently, you express this loss as a pressure change per unit length. In sprinkler practice using US customary units, the standard way is pounds per square inch of pressure lost per foot of pipe. This directly matches the typical pipe runs measured in feet and lets you estimate how much pressure will be lost over any length by multiplying the length (in feet) by the rate (psi per foot). Using metric units would give kPa per meter, which isn’t the convention in this context, and psi per meter would mix units in an uncommon way for the usual field calculations. psf per foot isn’t appropriate because psf is a pressure per area, not per length. So the expression that fits the common practice is psi per foot.