McAlpine Tunvalve Straight Through (Clear) with 19/23mm Universal Connections. This straight-through valve features a clear body for easy inspection and to detect blockages. The 19/23mm universal connections ensure compatibility with various plumbing systems. It functions as a non-return valve, preventing foul odours from entering the building, and is suitable for condensate discharge from boilers, air conditioning units, or cold water cisterns. Installation must be vertical and in a visible location for inspection. Not suitable for Pressure Release Valve (PRV) discharge.