A fitting is a detachable piece of pipe or tubing that either connects to another piece of pipe or tubing or connects two such pieces. Fittings are generally used in mechanical and plumbing operations for a number of different purposes. There are many different kinds of fittings, made from a variety of materials: some of the most common types are elbows, tees, wyes, crosses, couplings, unions, compression fittings, caps, plugs and valves.
Elbows
Elbows, also known as "ells," are used to change the direction of a pipe system. An elbow typically features a 45- or 90-degree bend, although other angles are also available. Elbows come in a variety of diameters and are generally threaded for connectivity. A common example of an elbow fitting in the home is the piece that extends from the wall of your shower to which the shower head connects.
Tees, Wyes and Crosses
Tee, wye and cross fittings are all used to combine or split pipe or tube sections. Their names describe the basic design of each: tee and wye fittings each have one input and two outputs (or vice versa), intersecting at 90 and 45 degree angles, respectively; cross fittings have one input and three outputs (or vice versa) that intersect at 90 degree angles. All three designs come in standard designs (in which all outlets/inlets are the same diameter) and reducing designs (in which one or more is a different size).
Couplings and Unions
Couplings and unions come in a number of different sizes and designs. The basic function of each is simply to connect two pieces of pipe or tubing. Therefore, couplings and unions are generally quite short fittings. The main difference between couplings and unions is that couplings are designed to be somewhat permanent and are often welded in place or secured by a series of bolts and nuts, while unions are designed to be easily removed at any time.
Compression Fittings
Compression fittings are generally made up of three pieces: a body, nut and gasket ring (or ferule). They use pressure to tighten connections, thereby preventing leakage. These fittings are used in many different industries, as well as many places throughout the house, such as in toilets and faucets.
Caps and Plugs
Caps and plugs perform basically the same function but in different ways. A cap, as its name suggests, is a cap that goes over the end of a pipe, creating a dead end. Plugs also stop up a pipe or tube system, but are plugged, like a stopper, into the end of the pipe.
Can You Use Teflon Tape on Gas Pipe Fittings?
When connecting gas pipelines and their fittings to a stove, grill or other connection, it is important to use Teflon tape designed for gas connections and not Teflon tape designed for water pipes. Teflon tape seals the gas fittings' threads and keeps leaks from developing. The Teflon tape for gas fittings is available at hardware, home improvement and plumbing supply stores.
Teflon Tape
Teflon tape for gas fittings, also known as gas-rated Teflon tape, is yellow in color and clearly states it is for gas lines and connections. The tape works on all gas line types, including butane, propane and natural gas lines. Gas-rated Teflon tape is thick, Underwriters Laboratories listed and has a temperature range of negative 450 to 550 degrees Fahrenheit. The tape cuts easily with a utility knife or scissors.
Where to Use It
Apply gas-rated Teflon tape only to the fittings' threads. Do not apply the tape to gas compression connections, the removable nuts and bolts used to connect two gas pipes together. Gas fittings are on the ends of gas lines and are not removable. Turn off all gas connections at the gas meter outside your home or business before disconnecting or attaching gas lines to appliances.
Gas Leaks
After applying the tape, connecting your gas lines and turning the gas back on, mix 2 teaspoons dishwashing liquid and 1 cup of water in a pot. Dip a cloth or rag in the soap solution and swab the solution on the gas fitting. If you see bubbles forming on the fitting, you have a gas leak. Immediately turn off the gas source and tighten the gas fitting. Then turn the gas back on and test the fitting again. If the solution is still bubbling, turn off the gas, disconnect the fitting and check the fitting for dirt, debris or damage. Clean the fitting thoroughly, and reapply gas-rated Teflon tape. Repeat the testing process. Have a professional replace the gas line if the soap solution continues to bubble.
Plumber’s Teflon Tape
If you use plumber's Teflon tape on gas pipe fittings, the tape will degrade over time and gas vapors will escape from the fitting. Plumber's Teflon is white in color and thinner than yellow gas-rated Teflon tape. Leaking gas pipes and fittings are dangerous and can cause an explosion. If you are uncomfortable applying gas-rated Teflon tape to gas fittings, contact a plumber or repairman specializing in gas connections and repairs to complete the gas pipe installation or repair.