A tap for providing an exterior water supply, comprising: - an outlet part, comprising an intake port adapted to receive a water flow when said tap is open, and comprising one or more flow channels adapted to guide said water flow towards an outlet side of said tap; - an anti-siphon device comprised in said outlet part, said anti-siphon device comprising: o circumferentially positioned vents; o a valve movable between a first and a second position, wherein: ▪ in said first position said intake port is opened and said vents are sealed from said one or more flow channels, and ▪ in said second position said intake port is closed and a passageway is formed between said vents and said one or more flow channels; wherein: - said outlet part comprises a sleeve mounted around said anti-siphon device, such that a circumferential slit is present between said sleeve and said anti-siphon device, said sleeve comprising a wall (406, 407) with varying thickness, and said wall comprising: o a cylindrical outer surface; o an upper wall part with a first thickness, and a lower wall part with a second thickness smaller than said first thickness, such that in mounted condition said circumferential slit is formed between said lower wall part and said anti-siphon device, - said sleeve comprises a recess, such that an air passageway is present from the exterior environment to said vents via said recess and said circumferential slit, - said outlet part comprises a connecter, said connector comprising a cylindrical part; CHARACTERIZED IN THAT: - in mounted condition, the outer surface of said cylindrical part of said connector is aligned with said cylindrical outer surface of said wall of said sleeve, thereby together defining a continuous cylindrical surface, and - in mounted condition, said cylindrical part of said connector and said sleeve are positioned close to each other, leaving an intermediate axial gap of less than 3 mm. - an outlet part, comprising an intake port adapted to receive a water flow when said tap is open, and comprising one or more flow channels adapted to guide said water flow towards an outlet side of said tap; - an anti-siphon device comprised in said outlet part, said anti-siphon device comprising: o circumferentially positioned vents; o a valve movable between a first and a second position, wherein: ▪ in said first position said intake port is opened and said vents are sealed from said one or more flow channels, and ▪ in said second position said intake port is closed and a passageway is formed between said vents and said one or more flow channels; o circumferentially positioned vents; o a valve movable between a first and a second position, wherein: ▪ in said first position said intake port is opened and said vents are sealed from said one or more flow channels, and ▪ in said second position said intake port is closed and a passageway is formed between said vents and said one or more flow channels; ▪ in said first position said intake port is opened and said vents are sealed from said one or more flow channels, and ▪ in said second position said intake port is closed and a passageway is formed between said vents and said one or more flow channels; - said outlet part comprises a sleeve mounted around said anti-siphon device, such that a circumferential slit is present between said sleeve and said anti-siphon device, said sleeve comprising a wall (406, 407) with varying thickness, and said wall comprising: o a cylindrical outer surface; o an upper wall part with a first thickness, and a lower wall part with a second thickness smaller than said first thickness, such that in mounted condition said circumferential slit is formed between said lower wall part and said anti-siphon device, o a cylindrical outer surface; o an upper wall part with a first thickness, and a lower wall part with a second thickness smaller than said first thickness, such that in mounted condition said circumferential slit is formed between said lower wall part and said anti-siphon device, - said sleeve comprises a recess, such that an air passageway is present from the exterior environment to said vents via said recess and said circumferential slit, - said outlet part comprises a connecter, said connector comprising a cylindrical part; - in mounted condition, the outer surface of said cylindrical part of said connector is aligned with said cylindrical outer surface of said wall of said sleeve, thereby together defining a continuous cylindrical surface, and - in mounted condition, said cylindrical part of said connector and said sleeve are positioned close to each other, leaving an intermediate axial gap of less than 3 mm.