The specific weigh of a liquid or a fluid is the weight per unit volume of the liquid. Specific weight is usually measured in Kg/dm3 or Kg/l (one L is 1 dm3).

Nel caso di liquidi o fluidi, il peso specifico è il peso dell’unità di volume del liquido stesso. Il peso specifico si esprime in Kg/dm3 o Kg/l (un L corrisponde ad 1 dm3)

Pressure means weight per unit of area (e.g. Kg/cm2). In case of liquids the pressure that the liquid exerts on a surface is given buy the product of the head of the liquid, multiplied by its specific weight. A Column of water of 10 m high is equivalent to approximately 1 Kg/cm2.

Per pressione si intende il peso per unità di superficie (per esempio Kg/cm2). La pressione che un fluido esercita su di una superficie è data dal prodotto della prevalenza del fluido stesso per il suo peso specifico. A livello del suolo la pressione è circa di 1Kg/cm2 (circa 1 atmosfera). 10 mca corrispondono a circa 1 Kg/cm2

The delivered power is the power delivered by the pump to the liquid. The value of this delivered power depends in three factors: flow, head, and specific weight of the pumped liquid. The higher these three factors, the higher is the power delivered by the pump. In order to pump a liquid a pump must be driven by a motor. The power that the pump needs in order to operate is called absorbed power.

Absorbed power is the power that the pump absorbs from the motor, to give to the liquid the deliver power. Not all the absorbed power becomes delivered power, as some power is lost through friction and to the function of the pump itself. The delivered power is always less than the absorbed power, and the ration between the two is a number always lower than 1. This number is known as the efficiency.