Instead of actually spilling out a fluid (which does not make much sense for a gas), it could instead create an airflow in the direction of the pipe.
Maybe even add your own Bulk Steaming recipes like Bulk Smoking, Blasting and Washing. Or just make it do the same as Bulk Washing.
The airflow could even slightly damage any entity that it gets in contact with (because steam is hot).
EDIT: From initial inspection you'd have to change the Steam fluid to a virtual fluid (like what Create does with the potion and tea fluid) and then add an effect handler that handles the creation of the airflow.
Though handling the airflow without a block implementing IAirCurrentSource is going to be tricky, so maybe it is wiser to just make Steam a virtual fluid and make a new pipe-like block (like a Pressure Release) that creates an airflow if left open ended (and if attached to another pipe or fluid container it could fill it with steam).