A tee, the most common pipe fitting, is used to combine (or divide) fluid flow. It is available with female thread sockets, solvent-weld sockets or opposed solvent-weld sockets and a female-threaded side outlet. Tees can connect pipes of different diameters or change the direction of a pipe run. Available in a variety of materials, sizes and finishes, they are used to transport two-fluid mixtures. Tees may be equal or unequal in size, with equal tees the most common.
Compression fittings (sometimes called lock-bush fittings) consist of a tapered, concave conical seat, a hollow, barrel-shaped compression ring (sometimes called a ferrule) and a compression nut which is threaded onto the body of the fitting and tightened to make a leakproof connection. Typically made of brass or plastic, stainless steel or other materials may be used.
Although compression connections are less durable than sweated connections, they are easy to install with simple tools. However, they take longer to install than sweated joints and sometimes require re-tightening to stop slow leaks which develop over time.