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recirculate water from waste valve on ram pump

 
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Is it possible to recirculate the water from a waste valve on a ram pump? could you plumb it back into a y in the delivery pipe?
 
pollinator
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Sure, but you'd have to add energy to it.

The velocity of the moving water, and it's in-compressible nature, are what provides the pressure/energy to make a ram pump work.  The waste water has had all that energy removed (it's went to powering the pump to lift the water).

To get the waste water back into the stream, you have to add energy back into it with some other kind of pump.  And of course that pump is going to have losses and waste energy, so all in all it's a losing proposition.

In simplified terms, the three laws of thermodynamics are:
#1 there is no free lunch.  You can't get something for nothing.
#2 You can't even break even, no matter what you are going to lose some energy.
#3 You can't even get close to even; the colder it is, the more energy you lose.
 
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So the question is, “Is it possible to recirculate the water from the waste value on a ram pump? Could you plumb it back into the delivery pipe?”
  The given answer is, “Sure, but you’d have to add energy to it.” And the explanation for this is that the “velocity of the moving water is what provides the pressure/energy to make a ram pump work” and that the “waste water has had all the energy removed” (by powering the pump to lift the water).
  However, isn’t the assumption that the ram pump is at a higher elevation than the water source?
  If so, why couldn’t a person thread into the waste water outlet a 45-degree elbow and then thread into the other-side of the 45-degree elbow, a down-hill running pipe that returns to a position just over (and not submerged in) the water source? Gravity would then provide the “energy” (pressure) necessary in returning the waste water to the source. This would eliminate the 90% or so of water loss (waste), thus effectively recirculating the water via a gravity-induced flow returning to the water source (which in turn feeds the delivery pipe running up to the ram pump).
  Just my hypothesis under the assumption that the ram pump is at a higher elevation than the water source.
  Yes? No?
  
—DL Tolleson
 http://www.dltolleson.com
 
pollinator
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I think the pump itself typically has to be lower than the surface of the water source. I think the energy is sourced from the water gravity feeding into it.
 
gardener
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Correct. A ram pump only works if it is lower than the water source.

Of course, if you have some use for water at a lower elevation than the pump, you can certainly collect the waste water and channel it to that location.
 
Dl Tolleson
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Hmm. Well, would a ram pump theoretically work if it were at the same level as the water source (positioned at the source or removed by a short distance but still at the same elevation), and then the "waste water" that was ejected a few inches (or more?) higher than the pump and source be piped back to the source?
  Presumably, due to downward air pressure (or hydrostatic pressure?), the waste water could not be "ejected" into a pipe that was too much higher than the elevation of the the pump because it would impact the effectiveness of the pump's valve. But under this revised scenario—with the the ram pump fed water from the same elevation as the source and the waste water ejected upward "X" amount of height, could there be enough fall to send the waste water back to a water source that is lower by the "X" height?
  I know there is math to determine how much fall in elevation is necessary to effectively move water down an incline, I just don't know if there is a minimum amount of "X" height that could avoid deleterious pressure on the pump while also using gravity to send the waste water back to the source (and while assuming the ram pump could be at the same elevation as the source).
  All speculative upon my part—If you see what I mean...

—Tolleson
 
Glenn Herbert
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Sorry, a ram pump will only work if it is lower than the source, by enough for the water in the supply pipe to pick up speed and push the ram plunger up with a "fountain" effect. When the plunger moves up, it suddenly cuts off the flow and the jump in pressure makes some of the water go through the exit pipe (there are technical terms for the parts that I don't recall at the moment). A check valve keeps that water from flowing back into the pump. The smaller the head (height difference between source and pump), the less water the pump can usefully move.
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