Question of pump head

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spiff

Feeder Fish
MFK Member
Dec 27, 2007
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If the pump is below the water level and pumps the water 2ft higher than the water level, but the outlet goes back down below the water level(so that it could maintain a syphon), what is the pump head?

Its zero, right?
 
No, the pump head would be roughly 2ft plus the distance that the pump is below the water level. Assuming I am understanding what you are saying, then the siphon created by the outlet of the pump being below the water level would work against the pump, not with it (i.e. the siphon is created from the higher water level to the lower water level).
 
nugpuffer;3474525; said:
No, the pump head would be roughly 2ft plus the distance that the pump is below the water level. Assuming I am understanding what you are saying, then the siphon created by the outlet of the pump being below the water level would work against the pump, not with it (i.e. the siphon is created from the higher water level to the lower water level).
Click to expand...


Are you sure? My thought is that if the whole line if full of water so that a siphon is possible, then pressure needed to go over what ever height that you have is zero. In other words, I would think the head height is 2ft initially, until the water went over the crest at which point it diminishes as the water goes back down the other side until eventually its zero as it goes under the water level and a siphon is possible.

Here is pict of what I mean..View attachment sip.bmp

If a siphon is possible all the way to the pump, it seems that head would be zero.
 
Yeah I kinda agree with you there Spiff.

The way i see it...

The head height is the difference between the surface level of the tank (or outlet of the pump, whichever is higher) minus the surface level of the water the pump is in.

Some clarification would be handy on this.
 
It would be zero (if I read the original post right; it's 2:00am here). The potential energy going up equals that coming down so the net energy is zero. Any distance below the water level is also equal to zero. And zero plus zero is zero.
 
Cool. Thanks for the replies. I figured this was the case but wasn't sure.
 
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