sparkyweasel
Member
- Joined
- 30 Jun 2011
- Messages
- 2,876
The head is the difference between the water level in the tank and the height of the return pipe/lily pipe/spray bar. If the return is submersed the head is zero. Having the canister on the floor doesn't matter. Gravity will bring the water in the return pipe up to the tank level even with the filter unplugged, the pump only has to lift it the rest of the way to the end of the outlet pipe.