A preparing and dispensing machine of a diluted beverage, comprising: a water inlet configured to be connected to the municipal water supply; a valve which has an inlet in fluid communication with the water inlet, an outlet, and which is activatable for enabling or shutting down the flow of water coming from the water inlet; a food concentrate mixture container which has an outlet of food concentrate mixture; an outlet of diluted beverage; a volumetric pump for aspirating internally thereof the food concentrate mixture and water, and for mixing them with one another, said volumetric pump comprising an inlet and an outlet; a first conduit which comprises: a first end which is connected to the outlet of the food concentrate mixture; and a second end which is connected to the inlet of the volumetric pump; a second conduit which comprises: a third end which is in fluid communication with the outlet of the valve; control means configured to activate the valve and the volumetric pump; a detecting unit of the water flow for detecting the quantity of water flowing from the water inlet, which detecting unit of the water flow is connected to the control means; wherein the control means are configured to activate the volumetric pump so as to regulate the flow of food concentrate mixture and water aspirated internally thereof as a function of the data received by the detecting unit; characterised in that: the preparing and dispensing machine comprises a user interface for commanding dispensing of a diluted beverage; the second conduit comprises a fourth end which is connected to an intermediate portion of the first conduit; the preparing and dispensing machine comprises a dispensing conduit for dispensing a diluted beverage which comprises: a fifth end which is connected to the outlet of the volumetric pump; and a sixth end which is connected to the outlet of diluted beverage in order to dispense the diluted beverage towards the outside; the preparing and dispensing machine comprises a third conduit which comprises: a seventh end which is connected to an intermediate portion of the dispensing conduit; and an eighth end which is in fluid communication with the outlet of the valve; the second conduit comprises a section narrowing for regulating the outflow velocity of the water in inlet into the first conduit. a water inlet configured to be connected to the municipal water supply; a valve which has an inlet in fluid communication with the water inlet, an outlet, and which is activatable for enabling or shutting down the flow of water coming from the water inlet; a food concentrate mixture container which has an outlet of food concentrate mixture; an outlet of diluted beverage; a volumetric pump for aspirating internally thereof the food concentrate mixture and water, and for mixing them with one another, said volumetric pump comprising an inlet and an outlet; a first conduit which comprises: a first end which is connected to the outlet of the food concentrate mixture; and a second end which is connected to the inlet of the volumetric pump; a second conduit which comprises: a third end which is in fluid communication with the outlet of the valve; control means configured to activate the valve and the volumetric pump; a detecting unit of the water flow for detecting the quantity of water flowing from the water inlet, which detecting unit of the water flow is connected to the control means; wherein the control means are configured to activate the volumetric pump so as to regulate the flow of food concentrate mixture and water aspirated internally thereof as a function of the data received by the detecting unit; characterised in that: the preparing and dispensing machine comprises a user interface for commanding dispensing of a diluted beverage; the second conduit comprises a fourth end which is connected to an intermediate portion of the first conduit; the preparing and dispensing machine comprises a dispensing conduit for dispensing a diluted beverage which comprises: a fifth end which is connected to the outlet of the volumetric pump; and a sixth end which is connected to the outlet of diluted beverage in order to dispense the diluted beverage towards the outside; the preparing and dispensing machine comprises a third conduit which comprises: a seventh end which is connected to an intermediate portion of the dispensing conduit; and an eighth end which is in fluid communication with the outlet of the valve; the second conduit comprises a section narrowing for regulating the outflow velocity of the water in inlet into the first conduit. the preparing and dispensing machine comprises a user interface for commanding dispensing of a diluted beverage; the second conduit comprises a fourth end which is connected to an intermediate portion of the first conduit; the preparing and dispensing machine comprises a dispensing conduit for dispensing a diluted beverage which comprises: a fifth end which is connected to the outlet of the volumetric pump; and a sixth end which is connected to the outlet of diluted beverage in order to dispense the diluted beverage towards the outside; the preparing and dispensing machine comprises a third conduit which comprises: a seventh end which is connected to an intermediate portion of the dispensing conduit; and an eighth end which is in fluid communication with the outlet of the valve; the second conduit comprises a section narrowing for regulating the outflow velocity of the water in inlet into the first conduit.