Plumbing fittings are essential components of a plumbing system, and include items such as tees, ells, and P-traps. A TEE is a type of fitting that connects three pipes together in a T-shape, allowing for the flow of water in two directions. An ELL is an L-shaped fitting that connects two pipes at a 90 degree angle. A P-trap is a U-shaped fitting that prevents sewer gases from entering a building by trapping water in the bottom of the U-shape.