# Water pumps

1. Sep 14, 2015

### thinkandmull

I read in the Britannica Encyclopedia yesterday that Rene Descartes rejected the idea that a water pump works because nature abhors a vacuum, and instead said that it works "by the weight of the water which counterbalances that of the air". I have an idea of the two contrary concepts opposed here, but its still a little fuzzy. Can someone help me understand what was at stake in those early discussions about classical physics and the water pump?

2. Sep 15, 2015

### Meir Achuz

I think that Descartes just didn't understand physics.

3. Sep 16, 2015

### Staff: Mentor

It is tough to translate philosophy to physics, but this sounds a bit like the "debate" between gauge and absolute pressure. A person who doesn't know the difference might not recognize that there is a limit to the value of negative gauge pressure (equal in absolute value to atmospheric pressure) and that absolute pressure can't go negative.

4. Sep 16, 2015

### Nidum

This argument possibly refers to a draw pump . That is a type of pump which has a vertical axis piston and cylinder arrangement with simple valves as used to draw water by hand from deep wells and bore holes . In use pump first draws a vacuum in the riser pipe and atmospheric pressure acting on water below ground then forces a column of water up into the pump body and ultimately out into a receiver (bucket) .

There is a limit to the depth which such a pump can raise water from . Simplistically limiting depth is equal to the height of a column of water which gives a static pressure at bottom of riser pipe equal to atmospheric pressure . That is about 32 ft . Practical limit is a bit less .