A pump must be primed in order to operate correctly, this means that the pump casing and inlet pipe must be filled with fluid and the air removed before operation. This needs to be done manually by the pump operator for a non-self-priming pump each time the pump is used to avoid damage from dry running. A self-priming pump removes these issues by completing the priming process automatically. The air is removed from the inlet pipework and pump casing when the pump is activated. Self-priming pumps are particularly useful for installations with a suction lift on the inlet side of the pump, the pump will draw the fluid up the pipework by creating a vacuum and removing any air that is present. In ideal conditions, a self-priming pump can lift fluids up to around 6m on the inlet side, however this figure is affected by fluid viscosity, pipework bore and other installation conditions, therefore this figure can be much lower from case to case. Allowances must also be made for wear and tear; suction lift capabilities will be much lower for older and worn pumps.