A device for delivering a liquid including a pump, and an anti-siphon valve external to the pump is disclosed. The anti-siphon valve includes an inlet channel connected to the outlet duct of the pump, and an outlet channel, between which a seat and a moving member are disposed that are suitable for co-operating together and that define, between the inlet channel and the outlet channel, a leaktight liquid flow zone. The moving member is suitable for going from an opening position making it possible for liquid to flow through the flow zone, to a closure position in which the moving member comes into contact with the seat of the valve and prevents any flow through the flow zone, the moving member being subjected to the pressure of a reference chamber that is not in fluid communication with the outlet channel.