Pressure Friction Head Loss (ft/100ft)


Volume Flow Nominal Pipe Size (inches)
US Gallons per Minute (GPM) Cubic Metre per Hour (m3/hr) 1/2 3/4 1 1 1/2 2 2 1/2 3 4 6
1 0.23 1.4 0.4 0.1            
2 0.45 4.8 1.2 0.4            
4 0.91 17.1 4.2 1.3 0.2          
5 1.14 25.8 6.3 1.9 0.2          
6 1.36 36.3 8.8 2.7 0.3 0.1        
8 1.82 63.7 15.2 4.6 0.6 0.2        
10 2.27 97.5 26.0 6.9 0.8 0.3 0.1      
20 4.54   86.9 25.1 2.9 0.9 0.4 0.1    
30 6.81     48.1 6.3 1.8 0.8 0.3    
40 9.08     82.0 10.7 3.1 1.3 0.4 0.1  
50 11.36       16.5 4.7 1.9 0.7 0.2  
60 13.63       23.5 6.6 2.7 0.9 0.3  
70 15.90       28.7 8.8 3.7 1.2 0.3  
80 18.17       36.8 11.4 4.7 1.6 0.4  
90 20.44         14.3 5.8 2.0 0.5  
100 22.71         16.5 7.1 2.4 0.6 0.1
125 28.39         25.9 10.8 3.8 1.0 0.1
150 34.07         35.0 14.7 5.2 1.3 0.2

1 gal (US)/min = 3.7853 l/min = 0.2271 m3/hr = 0.8327 Imperial gal (UK)/min. 1 ft = 0.3048m

For thermoplastic pipes velocities above 5 ft/sec should be avoided.