Under certain circumstances larger than expected pipe sizes may be seen through a CWS/HWS system when Special outlets are defined. This happens when Special outlets have loading unit values much higher than standard outlets.
Each Netsys CWS/HWS outlet has a connection size that must be set. Standard outlet types will default to the appropriate connection size. Details can be found in the Help files within the software. The default for Special outlets is a 15mm connection size but this needs consideration by the user.
Netsys sizes the pipes that feed outlets to the outlet connection size and for standard outlets this is fine. If a Special Outlet is defined with a high Loading Unit value and a 15mm connection size, this results in excessive velocity and therefore a high pressure drop. Netsys sizes downstream pipes back to the system marker based on flow rate, velocity and available pressure. Because of the high pressure drop in the outlet pipe there may be very little available pressure left and so downstream pipe sizes will be increased to ensure there is sufficient pressure at the outlet.
For Special Outlets it is imperative to set an appropriate outlet connection size for the loading units defined so a reasonable velocity and pressure drop are achieved in that section.