Method and device for pumping liquids using a pneumatic positive displacement pump

A method of pumping a liquid, especially sewage, with the aid of at least one operating tank of a pneumatic positive pressure displacement pump, which occurs in a sequence of two phases:

• a filling phase, during which a liquid is admitted into an operating tank through a pneumatically controlled inflow tank to displace the gas escaping out of it until it is filled;
• and a pumping phase during which the pneumatically controlled inflow valve located on the inflow conduit is closed, and then a compressed actuating gas is introduced into the operating tank, which causes the outflow return valve to open an the liquid is displaced from the operating tank until it is empty, characterized in that during the pumping phase the inflow valve (4) closure is controlled by the introduction of a control gas into the operating tank (2) of the pneumatic positive displacement pump (1) at a pressure lower than the pressure of the compressed actuating gas and lower than the hydrostatic pressure at the egress from the inflow valve (5) but at a pressure higher than the hydrostatic pressure at the ingress into the inflow valve (4), which causes the inflow valve (4) to close.