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Discussion Starter · #1 ·
I've wondered this question on and off a number of times......

Does the depth of water that a pump is in count against the Head Height of a pump?

In other words, If I wanted to pump, for example: up 2' from a 20g aquarium--Does it make any difference whether the pump is located at the top of the 20g or the bottom?

I realize that the extra plumbing (tubing/pipe) will create added resistance, but does the water depth itself matter?

I also realize that it would depend upon the pump. I'm not referring to something like a Mag 5, but more along the lines of a Via Aqua 480 (max head:4' 200gph).

Seems to me that the water depth would'nt matter--What say You?
 

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Technically, the deeper you go down into the H2O column with the pump, the less head you have because of the weight of the H2O pushing down on the inlet, so it kind of siphons to a small degree. Of course, that only applies just so far. You get to a point of diminishing returns really quickly. It barely makes a difference in real world scenarios. For practical purposes, head is the vertical rise above the pump outlet.

Tommy
 

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Discussion Starter · #6 ·
Technically, the deeper you go down into the H2O column with the pump, the less head you have because of the weight of the H2O pushing down on the inlet, so it kind of siphons to a small degree. Of course, that only applies just so far. You get to a point of diminishing returns really quickly. It barely makes a difference in real world scenarios. For practical purposes, head is the vertical rise above the pump outlet.

Tommy
I find that a bit confusing also, but I take:

For practical purposes, head is the vertical rise above the pump outlet.
to include variables like the resistance added by the hose, which I factored out of my initial question above.

So, would the "weight" of the H20 only effect the initial start up or would it carry through to continuous duty?
 

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I find that a bit confusing also, but I take:



to include variables like the resistance added by the hose, which I factored out of my initial question above.

So, would the "weight" of the H20 only effect the initial start up or would it carry through to continuous duty?

Sorry! I re-read my post. It does sound a LOT more technical than it needs to. There's next to no head on the pump up to the surface of the H2O, so your head is any vertical rise above that + friction losses from tubing elbows, etc. So if your pump has a rated head of 10', consider it at about 9' for frictional losses.

Tommy


Tommy
 

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Static head is measured from free surface of water to the other free surface. Basically, when the pump is not running, measure the distance between the two water surfaces. this is the static head. Although pressure head from a free surface acts on a pump, the pump can only "pump" what the volute capacity and rpm is set to.

summary to use: Total Dynamic Head (TDH) = Static Head + Dynamic Head

Dynamic Head = Head loss due to fiction of piping + Head Loss as a result of fittings (commonly charted as a function of equivalent lenght of pipe instead, in other words, a 90 degree elbow would have an equivlant length of pipe. this simplifies the calculations, since fitting losses are not standardized and are manufacturer dependent)

it should be noted that most aquarium setups do not account for the true dyanmic head, since the losses of the pipes and fittings are so minimal and can usually be neglected. But its always something to consider if you notice a pump or filter not working properly...
 
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