Venturi pumps, injectors, ejectors and eductors

We've had some severe weather blow through our area recently, and I've been thinking a lot about backup sump pumps.  It turns out that there is a lot of interesting physics in backup sump pumps.

It also turns out that the interesting physics is not as simple as I was hoping it would be.

This is a backup pump which requires no power (battery or otherwise) because it uses the Venturi effect to pull water out of the sump well. That sounded really interesting to me, so I sat down this morning and tried playing around with the Bernoulli equation and the continuity equation to see if I could come up with some interesting questions to ask my intro physics class next time we do fluid mechanics.

After struggling for five hours, and not coming up with anything remotely looking physically possible (47 meter pump extraction height? negative water pressure?), I've come to the conclusion that an intro level analysis (even making typical assumptions) is not possible.

After much searching through reference databases, I'm not sure I've even located a decent analysis of these pumps at an advanced level.

Since this pump is simple to conceptually understand, I'm having trouble figuring out why I can't locate a decent reference with the physics of how it works.  If anyone has seen anything on this, please let me know.