Howdo Spinky?!!
...
A powerhead is a (usualy) small pump that sits on top of a 1~1 1/4inch PVC tube in a fishtank to pump water from beneath the gravel, they are (usualy) submersed and (usualy
)have to be modded to run inline...
Try doing a fill a bucket test, see how many gallons/litres it will pump(without tube on the outlet side, tube will slowdown the flowrate) in one min' then multiply by sixty to give the Gallons/Litres~ PerHour measure...
Then get a long (6" plus) tube and connect to the outlet and hold upright/verticle and see/measure how far up the tube the pump lifts the water, this will be your maximum 'Head'...