Venturi Dosing

A system that mixes a concentrated product with water using the suction created when the water passes through a narrowing (Venturi effect), with no pump.

When water passes through a narrow throat, its velocity increases and its pressure drops. At that point a suction tube immersed in the product container is connected: the suction draws the product in and it mixes with the water. The ratio is set with a calibrated nozzle or valve of different diameters. This is the principle behind the dilution stations that fill buckets and sprayers, many foam units and some injectors in wash bays and hoses.

Its advantage is simplicity: it needs no electricity, has few moving parts and is cheap to install and maintain. Its main limitation is that the dilution depends on the water pressure and flow: if the mains pressure drops or varies, the concentration changes. That is why it should be checked periodically (by measuring the volume of product consumed or the concentration of the solution) and the nozzles cleaned, as they can become blocked with limescale or dried product. The installation must include a backflow prevention device so that the product cannot flow back into the drinking water supply.

Compared with a peristaltic or diaphragm pump, a venturi gives less precise dosing, but it is sufficient for preparing use dilutions from a concentrate. When an exact quantity has to be injected into a machine at the right moment in each cycle, as in industrial dishwashers or washing machines, dosing pumps are used.

More information: Dosing automation · Peristaltic dosing · Foam cleaning