Pipe fittings: Understanding the basic types and uses

Do you know your olet from your elbow (fitting)? If you're thinking of a DIY plumbing project, you’ll need to know what type of pipe fittings the job requires. It's time to brush up on your pipe fitting basics and impress your plumber friends.

Whether you’re replacing faulty plumbing pipes or installing new ones, you’ll need to know what type of pipe fittings your DIY job requires. These small but important pieces can help you complete your plumbing projects quickly and correctly. Brush up on your pipe fitting basics and impress your plumber friends by knowing your olet from your elbow (fitting).

Pipe fittings are an essential part of piping and plumbing systems. They’re the pieces that connect different pipe sections together (or to other components) and help run them where you need them to go—around corners, through ceilings or under the house.

Fittings that extend or terminate pipe lengths:

• Adapters connect two dissimilar pipes to each other by solvent welding, soldering or threading.
• Couplings connect two similar pipes to each other by solvent welding, soldering or threading.
• This category also includes adapters, sleeves, unions, caps and plugs.

Fittings that connect two or more pipes or change direction:

• Elbows change the direction of the pipeline. The most common angles are 90 and 45 degrees.
• Tees connect three pieces of piping in a T-shaped intersection. This lets you divert water to another line.
• This category also includes wyes, crosses.

Fittings that connect pipes of smaller sizes:

• Reducers connect two or more pipes of different sizes. There are reducer couplings, tees and elbows.
• Olets attach to branched connections when adequate reducing tees or crosses are not available.

Fittings that provide special connections or functions:

• Nipples allow two separate fittings to be connected at each end.
• Valves connect pipes together and control the flow of liquids.

The main ways pipe fittings connect are by threading or slip fitting.

• Threaded pipes screw together. Generally, metal pipes are threaded.
• Slip fit pipes use sleeves that slip into one another. Plastic pipes can be either threaded or slip fit.

These methods are organized as follows:

• Male threaded. Exterior threads screw into the inside of a larger diameter pipe end with internal threading.
• Female threaded. Interior threads are designed to receive male threaded pipe fittings.
• Male slip fit. No threads and are designed to slip into a slightly larger female sleeve.
• Female slip fit. No threads and are designed to slip into a slightly larger male sleeve.

Good to know!

Pipe fittings with one female end and one male end are called street fittings.

In general, a fitting should be the same material as the pipe to which you are fitting it. For example, use a PVC fitting with a PVC pipe. (There are exceptions where materials conforming to certain codes/standards can be used in pipes of another material.) Material options include:

Copper

• Used with hot- and cold-water applications.
• Commonly used in residential water supply lines and as a refrigerant line in HVAC.
• Comes in soft form (usually for refrigerant lines) and rigid form for water pipelines.
• Copper pipes are usually joined using a flare connection, compression connection and sweat or solder connection.

 PVC (polyvinyl chloride)

• The most common type of plastic, it’s rigid and comes in a variety of pressure ratings.
• For cold water applications only. Standard uses include cold water supply and drainage.
• PVC fittings are joined by a thread or solvent weld (glue) connections.

 CPVC (chlorinated polyvinyl chloride)

• Similar to PVC but suitable at higher temperatures and more ductile.
• Primarily used for residential hot- and cold-water applications.
• Often replaces a copper pipe in indoor applications.
• CPVC fittings are joined by a  thread or solvent weld (glue) connections.

 PEX

• For residential hot- and cold-water applications and as hydronic heating.
• Competitively priced and are easy to use.
• PEX is joined with plastic grip or metal crimp and clamp fittings.

 Good to know!

Make sure you select a material rated for the type of plumbing job you are doing. For example, some pipes are approved for pressurized air or gas, others potable or non-potable water. Always check local code requirements to make sure the materials you select meet current standards.

Before you buy, keep this handy checklist in mind:

• What type of fitting do you need (a pipe coupling, elbow, tee)?
• What material is best suited for your application?
• What thread size, pressure and temperature rating is needed?
• What tools do you need? Do you need any solvent cement or soldering tools?

Good to know!

Male threaded fittings are measured to the outside edge (outside diameter). Female threaded fittings are measured to the inside edge (inner diameter). There are many online references that can help you figure out the thread size you need. If you’re unsure, you can always ask an expert at your local home improvement store.

While the wide world of couplings and valves may seem confusing at first, a little knowledge goes a long way in proper pipe-fitting procedures. Developing an understanding of the basics will help you create a good foundation for your future DIY plumbing projects.