Water in High Rise Buildings

Question

Re: JJ's posting. High rise buildings have water tanks on the roof or on the top service floor. City water flows into the tank by main pressure or by booster pumps in the basement (depending on the hight of the building). Pump operation is controlled by the level in the tank. The water that comes out of your taps in the buidling flows by gravity from the storage tank. No P'saik Reisha at all.