Modelling emitters to represent leakages

Question

Dear Bentley, 
 I have assigned emitter coefficients to the nodes in my model to represent the leakages of the system. Emitter coefficient was calculated using the equation Q=k*P^n 
 However model results show a negative demand in some nodes where there are negative pressures. The reason I supposed is that the emitters create an inflow when the pressure is negative, which does not happen practically. 
 Is there a method to limit the minimum emitter discharge to 0, without giving negative discharges when nodal pressure goes negative? 
 Thank you, 
 
 Harsha

Tom Walski · Answer

You can install a check valve in the pipe just before the emitter to allow flow in only one direction.

Jesse Dringoli · Answer

If you have a situation where the emitter it not at the end of a pipe and you cannot use a check valve, you can either place a short pipe at a tee, add the emitter at a junction at the end of the lateral tee pipe, and place a check valve on that pipe, or you can consider using Pressure Dependent Demands (PDD). PDD is a bit more complex to set up, but you can fairly easily configure it to follow the emitter coefficient relationship, then have it apply to only a selection set of elements where you wanted the emitters. See: 
 Pressure dependent demands and negative pressure 
 Using Pressure Dependent Demands