How to Guide

48
Plastics Technical Manual
Pressure Flow
Friction loss through PVC pipe is normally obtained by using
the Hazen-Williams equation shown below for water:
f = 0.2083 x
(
100
)
1.852
x Q
1.852
C di
4.8655
Where:
f = friction head loss in feet of water per 100 feet of pipe
C = constant for inside pipe roughness (C = 150 for ABS
and PVC pipe)
Q = flow in U.S. gallons per minute
di = inside diameter of pipe in inches
Friction Loss Through Fittings
The friction loss through fittings is considered to be equivalent to the loss through a certain number of linear feet of pipe of
the same diameter as the fittings. To determine the loss through a piping system, add together the number of “equivalent feet”
calculated for the fittings in the system.
The chart below shows approximate friction losses, in equivalent feet, for a variety of Schedule 40 & 80 PVC and CPVC fittings
of different sizes.
The table on page 49 shows friction heads in feet and friction losses in psi for Schedule 40 pipe. It also shows the gallons per
minute (GPM) and velocities (in feet per second) for various pipe sizes.
Fitting
1
⁄2 ”
3
⁄4 ” 1 ” 1
1
⁄4 ” 1
1
⁄2 ” 2 ” 2
1
⁄2 ” 3 ” 4 ” 6 ” 8 ”
Tee (Run) 1.0 1.4 1.7 2.3 2.7 4.3 5.1 6.2 8.3 12.5 16.5
Tee (Branch) 4.0 5.0 6.0 7.3 8.4 12.0 15.0 16.4 22.0 32.7 49.0
90° Elbow 1.5 2.0 2.5 3.8 4.0 5.7 6.9 7.9 12.0 18.0 22.0
45° Elbow .80 1.1 1.4 1.8 2.1 2.6 3.1 4.0 5.1 8.0 10.6
Male/Female Adapter 1.0 1.5 2.0 2.75 3.5 4.5 5.5 6.5 9.0 14.0 —
Approximate Friction Loss For PVC and CPVC Fittings In Equivalent Feet Of Straight Pipe
Water Velocities
Water velocities in feet per second may be calculated as
follows:
V = 0.408709 Q
di
2
Where:
V = velocity in feet per second
Q = flow in U.S. gallons per minute
di = inside diameter of pipe in inches
DESIGN & ENGINEERING DATA