This is pretty easy actually: just hover over the pipe and keep cycling the Tab key until you see a boxed dotted line that surrounds the entire network of pipe/fittings/accessories. Then, left click once. This "selects" the system. Hit the delete key. This will remove the system and it will convert to an Undefined system. When you connect this piping network to a new system, it'll absorb the system it's conning into. Or, since it's Undefined, when you route new pipe you now have the option to select what system you want.

But if the System Classification is the same, you can select the System and change it to another. Storm Drain and Storm Overflow for instance can be interchanged easily without deleting the Piping System since they're both Sanitary System Classifications, etc.

Hope this helps.

-TZ

many many thanks TZ!!