A pump union is a type of plumbing fitting that is used to connect a pump to a plumbing system. It is typically made of a durable and corrosion-resistant material, such as brass or stainless steel, and is designed to be tightened by hand or with a wrench. The size of the union is typically measured in millimetres, and refers to the diameter of the fitting. In this case, a pump union 50mm is a fitting that has a diameter of 50 millimeters. It is used to connect a pump to a plumbing system with a pipe or hose of the same diameter.
