My question is: what does it mean phisical elevation in the properties of the tank. Is this terrain or something else?
Anytime you need a definition of a field you can either a) In the properties of the element single click to highlight the field name and then look at the bottom of the window for the definition (see screen shot below) or b) try to us the search tool in the help documentation and search for the term you need more information on. In this case 'elevation' under the physical properties section is defined as the ground elevation at the your tank. Notice that for junction, valves, and pumps this field is defined as the elevation at the centroid of junctions, valves, and pumps and for reservoirs this elevation is the hydraulic grade.
I hope that helps answer your question.
Answer Verified By: Boyan Borisov