Expressed in meters of liquid column or bar (pressure). In the latter case the pumped liquid does not exceed any change in level, but will brew exclusively at ground level at a given pressure. Symbol: H. Performance curve: Special graphic illustration that explains the benefits of the pump: the diagram shows the curve formed by the values of flow and lift height, indicated with reference to a particular type of impeller diameter and a specific model of pump. Low: Special pump installation, placed at a level below that of the vein from which water is removed: thus, water enters the pump spontaneously without any difficulty. Priming: Filling the pump or tubing to remove air present in them. In some cases, can be supplied also car bombs primed, or incorporate an automatic mechanism facilitates priming and therefore the implementation of the pump, which would be impossible otherwise, and very slow .

Cavitation: A phenomenon caused by an instability in the flow of current. Cavitation occurs with the formation of cavity in the pumped liquid and is accompanied by noisy vibrations, flow reduction and to a lesser extent, the performance of the pump. Raised by the rapid passage of small bubbles of steam through the pump: its collapse parts that slide. Viscosity is a property of the fluid pumped represents its ability to resist the displacement. The viscosity varies with temperature. Specific Gravity: Each fluid has a characteristic density. Water, which is used as a basis for comparison, conventionally has a specific gravity (or density) of 1 (a 4dc and at sea level).