## June 22, 2011

### 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.

Lee said...

Hey Andrew,

This is really interesting. We have a similar concern. Last June, the day we bought our place formally and got the keys, we opened the door on that rainy day to find 5" of water in the basement. Ugh.

A couple thousand dollars later of (needed) rennovation we have the basement where we want it, but we don't have a power outage backup plan.

So a few weeks ago I woke up in a sweat at 1am because the power had gone out and spent the next five hours napping 15 minutes and checking our sump pit alternately.

The physics of this are interesting, and I'd heard about the "water powered" pumps. I'm interested in any progress or discovery you make both scientific and practical =)

H said...

This is totally on my mind too!