Tees are among the most common types of fitting used in plumbing applications. Push fit reducing tees are used to join three pipes of different diameters together in a T shape in order to combine or divide the fluid inside. Like all other push fit plumbing fittings, they can be installed, removed and re-used with ease by simply inserting a pipe into them while using a pipe insert and twisting the plastic nut to lock it in place, then untwisting it if the pipe needs to be removed.