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What is the function of electric water pump, i.e does it push or pull water or both?

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That just depends on which way around you connect the two pipes to it. –  qftme Jun 22 '11 at 15:07
Depends on the pump. Question for the student: what limit applies to a suction pump that does not apply to a positive pressure mechanism? –  dmckee Jun 22 '11 at 15:08
Liquids flow because of difference of energy. To the lowest possible state. Energy can be described by pressure and the difference of pressure between INPUT and OUTPUT make it flow. –  Crowley Jun 22 '11 at 16:03
And for electric pump, there are Gear pumps, centrifugal pumps, piston pumps... All of them are based on different mechanism... –  Crowley Jun 22 '11 at 16:06
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2 Answers

Depending on the pump design it can push, pull or do both. In reality, all pumps are pushers, since even a pulling pump (e.g., sucking water up a drinking straw) is simply removing pressure on the pump side so that greater pressure on the pumped fluid at the other end of the line can push it into the pump.

Positive displacement pumps (e.g., gear pumps, peristaltic pumps and piston pumps) are typically considered "pushers," even though they are pulling the pumped material into the pump before pushing it out. You could use this intake to pump materials, in which case, I guess, you would have a "puller."

A centrifugal pump could be considered a pusher or puller, depending on which end the longest line is connected to. Then there is the electrodynamic pump, with no moving parts, which forces electrical current through the pumped media at right angles to an applied magnetic field, to induce a forward force in the conductive fluid itself: hard to characterize that one.

If any pump could be classified as a pulling pump it would be a pump working on the Venturi/Bernoulli effect. Pulling pumps which are open to the atmosphere have a theoretical pulling limit of 14.7 psi. This is because the real action is pushing by the atmosphere on the end away from the pump, and atmospheric pressure at sea level is 14.7 psi.

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I have a simple water pump that is an attachement to the Black end Decker electric tool. It is a small, 15cm or so disk, evidently rotating chambers inside to create a suction vacuum. So this one pulls the water.

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