Setting a junction class as a "Source" in an existing geometric network

Hello -

I've got an existing geometric network in which we originally had not intended to make use of flow direction using sources and sinks. Now it seems we may want to. So, my question is whether its possible to change/designate a simple junction feature class that's present in an existing geometric network as a "Source" without re-building the network.

Any insights would be much appreciated.

Thanks,
Ed