"Steve "Srfmon"" wrote in message
...
| Are you kidding? Who gave you this info?
| Head pressure is less when the height the pump has to carry the water
| lessened. Regardless if it is a closed loop or whatever.

DS is right, but only if the CL drain and return are both underwater. The
minute you raise the return above the water surface, you have head pressure.
But even then, it's only the distance from the water surface to the return
(or the top of the Upipe, for instance, that might go up and over the rim).
Head (in feet) is the distance from the water surface of the vessel the pump
draws from, to the water surface of the highest point it has to raise the
water to. In a closed loop, the water surface (think of it as "the amount of
water pushing down") is the same for the intake and output. Thus, head in
the return is cancelled out by (anti?)head in the drain. There will always
be friction loss, but not necessarily any vertical head pressure. By raising
the pump closer to the bulkheads, all that is done is to reduce the friction
loss.

Kev