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I read this article (link) but I'm having trouble seeing how a tiny impeller like this (link) can actually move water up my seven-story building. I understand it's connected to an electric motor, which spins it.

But does the spin on that impeller (at a high velocity) really create enough momentum to move water up seven or eight stories?

Are there other impellers or pumps along the way that help it? Or is it just that one pump attached to the boiler? (I live in an apartment complex with around 100 units.)

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    Approx. 1/2 lb./ft of pumping height means the pump only needs 35 psi (+ friction loss + working pressure needed) discharge to pump to the 7th floor. No big deal really, an impeller pump (actually called a centrifugal pump) can handle that no problem. Do some research on fluid dynamics and hydraulics, it's interesting.
    – Jimmy Fix-it
    Feb 25, 2015 at 6:19

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does the spin on that impeller (at a high velocity) really create enough momentum to move water up seven or eight stories?

It doesn't have to create momentum as it isn't throwing water ballistically. It just has to create a small difference in pressure.

Note that you ask about circulating water, not pumping it up into a tank. The pump does not have to overcome the head of water because the water is in a sealed circuit that also returns downhill. The weight of the water in the down-pipe balances the weight of water in the up pipe.

Cutaway photo of pump

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  • Great answer! So would this be the type of pump attached to a boiler? en.wikipedia.org/wiki/Flexible_impeller.
    – ktm5124
    Feb 24, 2015 at 21:58
  • @ktm5124: I've never taken one apart to see what it looks like. Those things run for decades without breaking down. I imagine they don't rely on flexible impellers that might wear out sooner. See youtube.com/watch?v=ECLQr3Z1pFk at 4:00 for what I imagine is more typical.
    – RedGrittyBrick
    Feb 24, 2015 at 22:10
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The answer to both of your questions is yes. They either use multiple pumps along the way, or they have one (or a couple) large pumps.

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  • The pump attached to the boiler is a rotary pump, correct? Also called an impeller? I linked an image of one in my post... is a tiny thing like that really capable of shooting water up 8 stories?
    – ktm5124
    Feb 24, 2015 at 20:52

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