Generally, the same place that the sprinkler systems drain to. More of a plumbing code requirement than fire (in my jurisdiction, at least). Call up the mechanical engineer that designed the drainage systems and ask.
Per the IPC, this could be considered clear water waste, similar to condensate, which is supposed to go to the sanitary system. Since the water is typically chlorinated, if it comes from a municipal source, it is not appropriate to discharge to grade in large quantities. I think this is due to the EPA not wanting highly (?) chlorinated water discharged to the environment due to its impact on the soils/plants/etc. How this is different than lawn irrigation - I do not know.
If the water is fresh(?), an argument can be made, and depending on the AHJ, and can be made successfully, to send it to the storm or discharge to grade.
However, most water in a fire suppression system is not fresh (looks very colored and slimey), so you may have difficulty getting it approved to dump to grade or directed to the storm.
The water in a sprinkler system looks black and slimy because of the coatings and such on the pipe. This water is different than the water emitting from the pump.
The water from the pump has just done a couple laps inside the impeller, then is routed thru the ½" or ¾" release. No worries of sliming there.
I like the comparison to lawn sprinklers. I may try to use that in the future.
