Pump system

A pump system comprising:

• a pump having a generally cylindrical pump housing, wherein the pump housing is arranged with a liquid inlet in a first end and a liquid outlet in a second end, and wherein the liquid inlet is oriented generally vertically downwards and the liquid outlet is oriented generally vertically upwards;
• a tubular membrane arranged inside the pump housing;
• a first passage arranged in a vicinity of the liquid inlet for introducing pressurized fluid between the tubular membrane and the housing, wherein the tubular membrane is arranged with an elasticity providing a local radial compression and a ring-shaped fluid compartment when a pulse of pressurized fluid is entered through the first passage, and wherein the ring-shaped fluid compartment travels along the housing bringing a volume of liquid with it;
• a second passage arranged in a vicinity of the liquid outlet for releasing the pressurized fluid;
• an expansion vessel operably attached to the liquid outlet for reducing pressure changes in the liquid caused by the action of the pulse of pressurized fluid;
• and
• a conduit attached to the liquid outlet and being oriented generally vertically for creating a liquid column, wherein an upper end of the conduit includes a first branch attached to the expansion vessel and a second branch that constitutes an outlet for the liquid.