water storage tank and control valve

[ceseng]

I am working on a water distribution modeling, the software I use is WaterCAD V8i.

on my model file, there are 7 Ground storage tanks, one pressure sustaining valve on the feed line of each GST.

what is the use of the pressure sustaining valve? I check the Bermad control valve catalogue, it is not a standard application for puting PSV on the feed line of GST. PSV is used to maintain the upstream pressure, usually on the discharge side of a pump to avoid pump overrun.

I am guessing if the PSV shall be altitude valve, as it make more sense for installing altitude valve before a storage tank. I am guessing the PSV is used to represent altitude valve on waterCAD, as there is no altitude value option on the WaterCAD, is this right?

any suggestion?

thanks.

 

[hydrae]

A PSV sustains back pressure. In the real world, A PSV is used on GST with altitude overide.

In the model world the altitude overide (in EPAnet) is automatic, the tank stops filling when full.
the PSV prevents the system pressure from dropping due to tank filling but allows the maximum amount of water available to fill the tank, without having to adjust a manual throttle valve.

Hydrae