The manometer holder tap with control flange is used to connect the network to any pressure measuring device. The function of this device is to section off the fluid from the pipeline to the measuring apparatus, to allow for its eventual replacement. When the tap is closed, residual fluid from the measuring instrument is discharged through a hole in its body, this is done to prevent accidental outflow of pressurized water when unscrewing it or, in near-zero temperatures, freezing of the fluid and consequent rupture of the measuring apparatus. The purpose of the flange with which the tap is fitted is to make it possible for the I.S.P.E.S.L. to check the pressure and, if necessary, the measuring apparatus; the measurements of this flange are in accordance with the requirements of the I.S.P.E.S.L. for the connection of its sample pressure gauge.