Spike's Calculators

Irrigation

Pressure Loss in Pipes from Friction

Calculate the pressure loss caused by friction in a section of the irrigation pipeline. When fluid flows through a pipe, friction between the fluid and the pipe walls causes a pressure drop along the length of the pipe. This pressure drop, known as head loss, can be calculated using the Hazen-Williams equation. The equation considers the pipe diameter, fluid velocity, fluid density and viscosity, and the roughness of the pipe surface. Minimizing pressure loss in pipes is essential as it can lead to decreased efficiency and increased energy costs in a system.

Pipe Material
Flow Rate US gal/min
Inside Pipe Diameter in
Pipe Length ft

Results:

Pressure Loss in 100 Feet of Pipe H2O/100 ft
Pressure Loss ft H2O
Pressure Loss psi

Calculation

  1. select the pipe material in use
  2. the flow rate of the water in US gallons per minute
  3. inside diameter of the pipe
  4. length of the pipe in feet

Results

  1. head loss in 100 feet of pipe expressed as expressed as H2O/100 ft
  2. total head loss in feet of water, expressed as ft H2O
  3. friction loss for the calculated amount of pipe in psi
Note
The unit "feet of water" (ft H2O) is a common way to express head loss and represents the height of a water column that would produce the same pressure as the head loss. It is often used because it provides a straightforward way to visualize and quantify the pressure or energy loss experienced by the fluid.


PVC and CPVC Pipes - Schedule 40
Nominal Size Outer DiameterInside Diameter
1/8"0.405" .249"
1/4"0.540".344"
3/8"0.675".473"
1/2"0.840"0.622"
3/4"1.05".825"
1"1.315"1.049"
1 1/4"1.66"1.38"
1 1/2"1.9"1.61"
2"2.375"2.067"
2 1/2".203"2.469"
3"3.5"3.068"
4"4.5"4.026"
5"5.563"5.047"
6"6.625"6.065"
8"8.625"7.981"
10"10.75"10.02"
12"12.75"11.938"
14"14"13.124"
16"16"15"
18"18"16.876"
20"20"18.814"
24"24"22.626"
PVC and CPVC Pipes - Schedule 80
Nominal Size Outer DiameterInside Diameter
1/8"0.405"0.195"
1/4"0.54"0.302"
3/8"0.675"0.403"
1/2"0.84"0.546"
3/4"1.05"0.742"
1"1.315"0.957"
1 1/4"1.660"1.278"
1 1/2"1.900"1.500"
2"2.375"1.939"
2 1/2"2.875"2.323
3"3.500"2.900"
4"4.500"3.826"
5"5.563"4.813"
6"6.625"5.761"
8"8.625"7.625"
10"10.750"9.564"
12"12.750"11.376"
14"14.000"12.500"
16"16.000"14.314"
18"18.000"16.126"
20"20.000"17.938"
24"24.000"21.564"
PVC Class 160 IPS Plastic Pipe
Nominal SizeOuter DiameterInside Diameter
1/2"0.840"0.696"
3/4"1.050"0.910"
1"1.315"1.175"
1-1/4"1.660"1.512"
1-1/2"1.900"1.734"
2"2.375"2.173"
2-1/2"2.875"2.635"
3"3.500"3.210"
4"4.500"4.134"
6"6.625"6.084"
8"8.625"7.921"
10"10.750"9.874"
12"12.750"11.710"
14"14"12.860"
16"16"14.696"
18"18"16.532"


PVC Class 200 IPS Plastic Pipe
Nominal SizeOuter DiameterInside Diameter
1/2"0.840"0.696"
3/4"1.050"0.910"
1"1.315"1.169"
1-1/4"1.660"1.482"
1-1/2"1.900"1.700"
2"2.375"2.129"
2-1/2"2.875"2.581"
3"3.500"3.146"
4"4.500"4.046'
6"6.625"5.955"
8"8.625"7.755"
10"10.750"9.666"
12"12.750"11.464"
14"14"12.588"
16"16"14.384"
18"18"15.246"
PVC Class 315 IPS Plastic Pipe
Nominal SizeOuter DiameterInside Diameter
1/2"0.840"0.696"
3/4"1.050"0.874"
1"1.315"1.101"
1-1/4"1.660"1.394"
1-1/2"1.900"1.598"
2"2.375"1.983"
2-1/2"2.875"2.423"
3"3.500"2.948"
4"4.500"3.794"
6"6.625"5.583"
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