Calculating how powerful of a pump to use

Is there a way to calculate the power a pump will need to be in to reach a point with a certain amount of waterflow, taking into account a rise over the aquarium wall and a descent to a container, and then back up into the aquarium?

 

Most all pumps will give you a head rating. Head=
The pressure in a column of liquid. Pressure will increase as the height of the column increases. Head refers to the height in feet; pressure refers to the psi (pressure pounds per square inch).


Like this.

 

here are a few things to think about...total drainage, coeficient of friction, and head pressure.

Total maximum drainage from overflow:

3/4"-700 gph.
1"-1000gph.
1 1/4"-1200gph.
1 1/2"-1500gph.

*Dersa style overflows will allow up to 20% higher maximum flow over a standard standpipe.

Coeficient of friction:

every 22, 45, or 90 degree bend adds friction slowing maximum possible drainage
90 degree bends can also result in bubbles gurguling trying to escape drag

Head Pressure:

Every vertical foot=1ft head pressure
Every 3 horizontal feet=1ft. head pressure
Every 90degree bend =1.5 ft. head pressure.

This will effect the total pumping volume, it is easier to get an oversized pump & tone it back with a ball valve