The McAlpine VP1W Ventapipe 25 Air Admittance Valve with 1.5" BSP thread on outlet is a plumbing component used in drainage systems. The purpose of the valve is to allow air to enter the drainage system when needed, which helps to prevent water from being siphoned out of traps or pushed out of the system by pressure changes. The Ventapipe 25 valve is designed for use with 1.5" diameter pipes, and it features a BSP (British Standard Pipe) thread on the outlet. This thread is a common type of thread used in plumbing in the UK, and it allows the valve to be easily connected to other components in the drainage system. The McAlpine VP1W Ventapipe 25 valve is a reliable and durable option for air admittance in drainage systems. It is made from high-quality materials and has been rigorously tested to ensure it meets industry standards for performance and safety. 1.5" BSP thread on Outlet A1 rated Air flow capacity of 3 l/s For full information on Air Admittance Valves please see below | McAlpine VP1W Ventapipe 25 Air Admittance Valve with 1.5" BSP thread on outl in White