The McAlpine Waste Valve 1.1/4" Tundish Macvalve-3 is a plumbing component used in waste and drainage systems. The valve is designed to allow waste water to flow out of a plumbing system while preventing gases and odors from entering the living space. The valve includes a tundish, which is a small device that allows air to enter the system and prevents the waste water from siphoning back into the plumbing fixtures. The Macvalve-3 model is specifically designed for use with a 1.1/4" waste pipe. It is made by McAlpine, a leading manufacturer of plumbing products in the UK.