Pumps
UNIVERSAL pumps will work in any situation whether above or below the water tank level
POSITIVE head pumps must be situated below the outlet from the water tank so that there is always a positive head of water flow to the pump.
UNIVERSAL and POSITIVE head pumps can be used to increase pressure to just a shower, the whole bathroom or several locations in the house. However you can now buy a Mains Pump which will boost the mains supply to the complete house.