Suction Head and Delivery Head in Pumps

Suction Head
The suction head refers to the difference in level between the water  in the sump to the centre line of the pump.  It is expressed in metres

The Delivery head
The Delivery head is the difference in level from the water level in the tank to the centre line of the pump.  It is expressed in metres

Static head
The difference between the water level of the tank to the water level of the sump when the pump is not running is called the Static head.  Its unit is metres.