Filter pump height?

I have a 50 gallon tank and am using a Fluval404 canister filter to
filter and circulate the water through a reverse undergravel setup. I
have the Fluval mounted in the cabinet that the tank sits on, so the
rotor for the pump is about three feet below the surface of the water.
I've always thought that since it is a closed system, the height of
the water above the pump is not an issue. A friend insists that if I
raise the pump to reduce the "head" that it will pump more
efficiently.

What's the truth?

Thanks very much.

Dave Smith wrote:
>
> I have a 50 gallon tank and am using a Fluval404 canister filter to
> filter and circulate the water through a reverse undergravel setup. I
> have the Fluval mounted in the cabinet that the tank sits on, so the
> rotor for the pump is about three feet below the surface of the water.
> I've always thought that since it is a closed system, the height of
> the water above the pump is not an issue. A friend insists that if I
> raise the pump to reduce the "head" that it will pump more
> efficiently.
>
> What's the truth?
>
> Thanks very much.

You are correct, lift isn't an issue with a closed system. Only
loss due to friction (line length and diameter) and fittings.

Paul