Which three factors determine the size of a service pipe?

• A. The quantity of water required, the residual pressure required by customer, and pressure of the main
• B. The diameter of the main
• C. Distance to customer
• D. Material of the water main

Answer: (A)

The size of a service pipe is determined by how much water the customer needs, the pressure the customer must have at the point of use, and the pressure available from the water main. If the customer requires a larger flow, the service pipe must be able to carry that higher demand without dropping the pressure below what’s needed, which pushes for a larger diameter. If the residual pressure required at the customer is high, the pipe must maintain enough pressure along the run, again favoring a larger size to minimize loss. Finally, the pressure supplied by the main sets the starting head; if the main has limited pressure, the service line must be sized to deliver the required customer pressure after accounting for friction losses, which can also influence the chosen diameter. Distance to the customer affects losses along the line, but the three primary determinants themselves remain the demand, the required customer pressure, and the main’s available pressure.