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What are Pipe Fittings?

According to Home Questions Answered:

If you’ve ever had to replace the U-turn or “trap” under the bathroom sink, build your own sprinkler system, or perhaps run water and gas lines to install a washer and dryer, chances are you already know all about pipe fittings. Pipelines, whether steel, copper, plastic Acrylonitrile Butadiene Styrene (ABS), or Chlorinated Polyvinyl Chloride (CPVC) are assembled in pieces with these items. They allow the lines to run around a corner, under a house, over a ceiling, or anywhere else you need them to go.

For example, if a pipeline has to be laid around a corner, the pipe is cut just short of the corner and an elbow fitting is placed at the end of the pipe. The elbow is a short length of pipe with a 90-degree bend. It allows pipes to be securely connected at both ends, providing a clean turn. Bulkheads and spigots are other types of pipe fittings.

Pipe fittings connect to pipes in one of two ways: by threads or by slip fit. Metal pipes are threaded, while plastic pipe can be threaded or slip fit. As the names indicate, threaded pipes screw together to connect, while slip fit pipes use sleeves that slip into one another. They are organized by male and female connectors as follows:

  • Male threaded: Threads are exterior, made to screw into the inside of a larger diameter pipe end with internal threading.
  • Female threaded: Threads are interior, made to receive male threaded fittings.
  • Male slip fit: No threads, made to slip into a slightly larger female sleeve.
  • Female slip fit: No threads, made to receive a narrower male slip fit.

The ends of pipe fittings are slightly larger than the rest of the pipe to accommodate connections without narrowing the inner diameter (ID) of the pipe. This keeps flow consistent. They are identified by pipe material, inner and outer diameter of the pipe, and the type of fitting — threaded or slip, male or female.

When purchasing pipe fittings, be sure to note that a fitting can have two different connector types. One end of the fitting might be male threaded, the other female threaded. In the case of plastic fittings, one end might be male slip while the other end is threaded. Fittings might also have matching ends — a variance to accommodate any requirement.

If repairing existing pipe or installing new pipe, be sure to use materials rated for the job. Some pipes are approved to carry pressurized air or gas, others potable or non-potable water. For example, PVC is often used for above-ground drainage applications and sprinkler systems, while CPVC is rated for hot and cold potable water. ABS, on the other hand, is a heavy-duty plastic pipe used for underground drainage and sewer applications. It’s therefore important to replace piping with the same material or material of an equal or higher rating.

Various kinds of sealers are used with pipe fittings to guarantee a tight, leak-proof fit. Sealing tape is often used with threaded pipes and can be rated as waterproof. Plumber’s tape, as it’s sometimes called, is an elastic gummy tape that is tightly wrapped around the male threads several times before screwing the fitting into the female end. The tape forms a good seal between threads. Slip fit fittings use quick drying solvent cement that “melts” plastic fittings into one another. Some people prefer slip fit pipes and cement because they are easy to connect and form a very good bond. One disadvantage, however, is that the pipe cannot be disassembled later, as with threaded pipes.

Pipe fittings are available at all home improvement centers and everywhere plumbing materials are sold. If you are unsure about what type of materials you need, consult someone at your local home improvement or plumbing store. Note that running a gas line might require a permit in some cities, so check local laws. If installing a sprinkler system, beware of underground cables or city water lines running to the premises. It is wise to check plans and consult with the local water and telephone or cable companies.

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