Often as part of a Cold Water System (CWS) there will be a supply to a related Hot Water System (HWS). Thus there is a requirement to take the demand of the HWS into account.
Firstly, you will need to create a Netsys HWS project to calculate the demand of your HWS alone.
Then, when modelling your CWS, to take the HWS into account you simply need to take the design flow calculated from the results in the HWS project and enter this into your CWS project as a Special outlet with Continuous Flow, in litres per second.
The above principles also apply should you wish to represent a series of outlets (e.g. a whole floor / zone) in one single outlet.
You should not attempt to specify this cumulative demand as a single, large Loading Unit
Doing so is not in accordance with BS EN 806 (detailed here) for two reasons: