You could possibly create Pipe Types that are the same names as the System type, ie: Chilled Water Pipe Type, Domestic Cold Water Pipe Type, Sanitary Vent Pipe Type, and so on. Then the Filter could sort based on the pipe type name. The main gotcha is to duplicate all the fittings so as to have the type name on the fitting itself, ie: Sanitary Tee, Domestic cold water tee, and even the Conduit tee for the electricians to use.