Hello, I'm new to WaterCAD and am struggling to solve what I thought was a relatively simple problem.

I have an existing 8" PVC waterline that I am connecting a new fire hydrant to via a new 8" PVC. The new FH is ~700 feet away from the existing line, and at the point of connection (junction), I have 1950 gpm with a residual pressure of 20 psi. I am trying to determine the available fire flow at my proposed hydrant.

Right now my model consists of a reservoir, a junction, and the hydrant; and I filled out the Base Fire Flow alternative. I can manipulate the length of pipe between my reservoir and junction to get the desired GPM at the junction, but I can’t figure out how to set the residual pressure at the junction to 20 psi. Right now I’m getting a higher residual pressure at the FH than the junction, which doesn’t make sense. Any help would be greatly appreciated!