Normally submersible pumps produce more pressure so it pumps more water to produce a higher head. When the liquid in the tank is higher, the pump of water also higher and able to pump the water in vertical discharge pipe because of the head exerted by the liquid in the suction tank.

The Head is the main term in submersible pumps and it is useful to increase the pump. There may be some range of head for getting increasing. Head is nothing but a height in which water rising up. This is called the head. It is represented simply by meters or metre of the liquid column.

You can increase the maximum head of a submersible pump by reducing the flow then head will increase. Because of this friction losses may occur. But along with head pressure also increases. Increasing the level of liquid in the tank, the head also increases. This is the explanation of increasing the maximum head of a Submersible Pumps.