Pump Head Measurement

[demasoni]

Ok, I'm a newbie to the forum and I'm not sure this is the appropriate place to post a stupid question, but here it goes.....

Where do you measure pump head from? The pump itself (mine is 42" under the surface) or the surface of the water?

I have a new pond in the front yard and after initial testing of my diy filter box and a maxflo 2000 pump, I don't think it makes a bit of difference, but it is a nagging question to me...

 

[Conner]

You measure from the pump to the surface of the water (or however high the plumbing has to go before it gets where its going).

If you're pump is at the bottom of the pond, pumping up to the skimmer, and the pond is 3' deep, then it would be 3' of head. You also have to factor in horizontal distance. Every ten feet or so of horizontal distance will add 1' of head height to your pump.

 

[Pharaoh]

Conner pretty much nailed it.

 

[mrunlucky07]

Where do you measure pump head from? The pump itself (mine is 42" under the surface) or the surface of the water?

The surface of the water the pump is in. The depth of the pump in the water is NOT part of head measurement. Turn the pump off and gravity will push the water up the pump discharge to surface level for free.

From this page http://www.pondsolutions.com/friction-loss.htm
"As a reminder, the DEPTH of the pond where the pump is located does not count toward the 'head' or 'lift' of the pump. The 'head' or 'lift' of the pump is determined by the distance ABOVE the water's surface."

Every ten feet or so of horizontal distance will add 1' of head height to your pump.

As a rough rule of thumb thats a good way to look at it.

Pipe size and flow are two important parts though, especially at higher flow rates.
From the chart on the above page - 2500gph is a little over 40 gpm, so with 10' of pipe you would loose 28" of head for every 10' with 1.25" pipe and only about 3.5" head for every 10' with 2" pipe.

 

[Conner]

The water is still exerting back pressure on the pump, so there will be some loss of gph rating no matter what, maybe just not as much as I stated.

 

[Burko]

No. The only extra work the pump has to do is in frictional losses.

Pressure due to head height must start at the surface.