The following graphic will help you when determining pipe friction characteristics and calculating the correct pipe diameters.

### Circulation pumps

Example
Q = 25 m³/h, 20 m plastic pipe with DN 50 ≙ d 63: DN 65 ≙ d 75
Expected loss reading as seen in the table (Hv = 18.00 m per 100 m): 5.00 m per 100 m
Expected loss
20 m pipe (x 10/100) (Hv = 3,60 m): 1.00 m
Monitored flow speed (v = 3.40 m/s - too high): 2.00 m/s - acceptable The pressure loss in this example is valid for clear water at 20 °C and for liquids of similar kinetic viscosity and for new PVC U-pipes. Pressure loss (mWS)/Flow rate Q (m³/h)

### Counter swim units

To achieve an almost loss free operation of counter swim units use the table below to dimension the pipe diameter.

The example is based on:
Suction line (S) with two elbows and the pressure line (D) with three elbows.

 Q (m³/h) Length of pipe 5 m 7.5 m 10 m 45 Suction line (S) d 125 d 125 d 125 Pressure line (D) d 125 d 125 d 125 58 Suction line (S) d 140 d 140 d 140 Pressure line (D) d 140 d 140 d 140 75 Suction line (S) d 160 d 160 d 160 Pressure line (D) d 140 d 140 d 140