Separation of Piping Systems

[IMCornish]

How do you stop one piping system, where it connects to another, from changing the identity of the later to its own?  For instance I have two foul water systems, the first being above ground, within a dwelling having a vertical pipe which connects with the second, below ground system. They both have differing pipe types but share the same pipe segments.  Should the segments be different?

[asommer]

You can split the pipe with a union between them, but they will take on the same system.  To separate these, you would have to copy a union and un-link the connectors.  You would need this at every change of system.

[IMCornish · Accepted solution]

This sounds complicated to me and far from being a 'real world' situation.  However, I have solved the situation by ensuring that each adjoining system has a different pipe segment type.  Previously this was not the case and therefore it would appear that the segment would inherit the adjoining systems identity.