How can I use US Survey feet as the unit for coordinates and lengths?
First, you will need to be using version 08.11.00.44 or greater.
Go to Tools > Options > Units. Click the dropdown next to "Coordinate" and change it from "ft" to "US Survey Ft".
Click OK and your X/Y Coordinates will be US Survey feet. If you'd like pipe lengths, elevations, etc to be in US Survey feet, change their units as well. For example in the properties of a conduit, right click on the "Length (Scaled)" field, choose "units and formatting", then select "US Survey Ft". as the unit.
Setting units for data import and export (LandXML, Inroads, etc)
Changing units or converting units for elements and profiles