Calculation to Determine Internal Diameter of Pipe for a Pumping System

In order to determine internal diameter (ID) of pipe for a pumping system, there are 2 parameters that we need to know which are flow in the pipe (Q), and its velocity (V). The formula is as shown in the picture below.

Q is the required flow for the system that we design, while V is determined based on the purpose of the system. The V value can be determined using the design standard that available such as:

  • For a piping system inside the building, recommended V is not more than 3 m/s: Refer to BS6700 Standard (Design, installation, testing and maintenance of services supplying water for domestic use within buildings and their cartilages;
  • For a piping system outside the building, recommended V is from 0.5 m/s to 2 m/s: Refer to BS EN 805 (Water supply requirements for systems and components outside buildings); and
  • For a irrigation or raw water pumping system, recommended V is not more than 2 m/s for suction line, and not more than 3 m/s for the delivery line: Refer to DID Manual Volume 8.