2025 Nelsen Corporation Catalog - Catalog - Page 447
Pipe Friction Tables 17
4: If the well and pump do not have the capacity to meet the
Peak Demand, an extra large pressure tank, or a 2-pump
system may be necessary. In a 2-pump system, the well
pump pumps into a storage tank at a rate which does
not exceed the well capacity. This pump is controlled by
a switch actuated by water level in the storage tank. A
second pump, of the centrifugal “booster” type, pumps
from the storage tank to the pressure tank. It is actuated
by a pressure switch. Consult your representative on
specific installations requiring supplemental water storage.
EXAMPLE:
FRICTION LOSS: Pipe friction is the resistance to flow
created by the interior surface of the pipe through which a
liquid is moving. The smaller the diameter of the pipe, or
greater the rate of flow, the greater the amount of friction
(friction loss).
(A) 100 ft. of 2" plastic pipe with one (1) 90° elbow and one
(1) swing check valve.
Friction loss is expressed as feet of head in 100 feet of pipe
and will vary depending upon the material of which the pipe
is made. The following charts show friction losses in steel,
copper, and plastic pipe, Pipe size should be sufficiently
large so that not more than 10% of the total dynamic head is
in friction loss.
90° elbow — Equivalent to
5.5 ft. of straight pipe
Swing Check — Equivalent to
13.0 ft. of straight pipe
100 ft. of pipe — Equivalent to
100.0 ft. of straight pipe
Technical & Engineering
to find the tank size required, which is 150 gallon Plain steel,
80 gallon Wafer, or 75 gallon Bladder or Diaphragm types. If
a standard tank is not available in the indicated size use the
nest larger standard size.
= 118.5 ft.
Total equivalent pipe
Figure friction loss for 118.5 ft. of pipe
(B) Assume flow to be 80 GPM through 2" plastic pipe.
1. Friction loss table shows 10.9 ft. loss per 100 ft. of pipe.
2. In step (A) we have determined total feet of
pipe to be 118.5 ft.
3. Convert 118.5 ft. to percentage 118.5 ÷ 100 = 1.185.
4. Multiply 10.9 x 1.185 = 12.9165 or 12.92 ft. = Total friction
loss in this system
Equivalent Number Of Feet Straight Pipe For Different Fittings
Size of Fittings, Inches
90° Ell
45° Ell
Long Sweep Ell
Close Return Bend
Tee-Straight Run
Tee-Side Inlet or Outlet
Globe Valve Open
Angle Valve Open
Gate Valve - Fully Open
Check Valve (Swing)
Check Valve (Spring)
1/2"
1.5
0.8
1.0
3.6
1.0
3.3
17.0
8.4
0.4
4.0
4.0
3/4"
2.0
1.0
1.4
5.0
2.0
4.5
22.0
12.0
0.5
5.0
6.0
1"
2.7
1.3
1.7
6.0
2.0
5.7
27.0
15.0
0.6
7.0
8.0
11/4"
3.5
1.7
2.3
8.3
3.0
7.6
36.0
18.0
0.8
9.0
12.0
11/2"
4.3
2.0
2.7
10.0
3.0
9.0
43.0
22.0
1.0
11.0
14.0
2"
5.5
2.5
3.5
13.0
4.0
12.0
55.0
28.0
1.2
13.0
19.0
21/2"
6.5
3.0
4.2
15.0
5.0
14.0
67.0
33.0
1.4
16.0
23.0
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3"
8.0
3.8
5.2
18.0
4"
10.0
5.0
7.0
24.0
5"
14.0
6.3
9.0
31.0
6"
15.0
7.1
11.0
37.0
17.0
82.0
42.0
1.7
20.0
32.0
22.0
110.0
58.0
2.3
26.0
43.0
27.0
140.0
70.0
2.9
33.0
58.0
31.0
160.0
83.0
3.5
39.0
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