Applies To
	Product(s):	SewerGEMS, CivilStorm
	Version(s):	All
	Area:	Modeling

 

Problem

What does the following user notification mean:

"One or more junctions are pressurizing all conduits; or conduits are in Preissmann slot at this location for this time-step."

"Conduit is operating under pressure."

OR

How does the implicit solver (SewerGEMS) transition from pressure flow to gravity flow and vice versa? 

Solution - dynamic solvers in SewerGEMS and CivilStorm

This message is generated when a pipe's HGL is above the top elevation.

The dynamic solvers available in SewerGEMS and CivilStorm do not distinguish between conduits and pressure pipes in the model, so this message may be generated when pressure pipes exist in the system. You can view profiles of the system to see the HGL across the system, as a way to see any gravity pipes in the model are surcharging.

For more information on Preissmann slot method used in this situation, there are topics about this in the Help documentation. Search for the term "Preissmann slot" or "Pressurized Flow".

Solution - GVF-Convex (SewerCAD) or GVF-Rational (StormCAD) solvers

The "Conduit is operating under pressure" message can occur with these solvers when the hydraulic grade line is above the top of the pipe and is just informational, not necessarily a problem. It is shown as a way to alert you that at least part of the conduit is pressurized. The software is able to handle this situation, but it is something the user may want to check. 

Create a profile of the element in question and you can observe if some or all of the pipe is pressurized, then take action, or choose to ignore the message.