Max flow from 2" inlet?

[Jaws]

I was just wondering what the maximum amount of water a 2" inlet could handle? Reason I'm asking is I'm going to need to pump a lot of water from my sump, some of which will be to the display tank which will have about 15' of head and some of which will be to a frag tank and a refugium which will only be about 4' each of head. I have a hammerhead pump and i'm wondering if I can "T" off the 2" bulkhead in the sump to add another return pump if the hammerhead isn't enough flow for the entire setup. Thoughts?