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A pipe nipple is a short, stand-alone piece of pipe, threaded on both ends, used to join two fittings, valves, or other components together in a piping system. Unlike a standard length of pipe, a nipple typically measures less than twelve inches and is manufactured specifically to connect two female-threaded fittings that would otherwise sit too close, or too far apart, to join directly. The defining trait of a pipe nipple is that it has male threads on both ends, with little or no unthreaded shoulder in between.
Pipe nipples appear in nearly every type of fluid or gas handling system, from residential plumbing to industrial steam lines, compressed air networks, irrigation setups, and chemical processing equipment. Because they come in dozens of lengths, diameters, and thread configurations, choosing the right nipple style affects leak resistance, pressure rating, and how easily a line can be serviced later.
The Main Types of Pipe Nipples
Pipe nipples are classified primarily by their length and thread pattern. Each style solves a different spacing or assembly problem, and recognizing the differences prevents costly reordering on a job site.
Close Nipples
A close nipple is threaded along its entire length, with no visible unthreaded section in the middle. This style is used when two fittings need to sit directly against each other with virtually no gap. Because there is no shoulder to grip with a standard wrench, installers typically use a nipple wrench or pipe wrench positioned carefully on the threads, which means close nipples see more wear at the thread root than longer styles.
Shoulder Nipples
A shoulder nipple has threads on both ends with a short unthreaded section, the shoulder, in the middle that a standard pipe wrench can grip safely. This shoulder is usually around one inch and protects the threads from being damaged during installation. Shoulder nipples are the most common type specified in commercial plumbing and HVAC drawings because they balance compact size with safe handling.
Long Nipples and Running Nipples
When a connection needs to span a wider gap, contractors use long nipples, sometimes called running nipples, which can extend from four inches up to twelve inches or more. These are essentially short sections of pipe threaded on both ends and are ordered by exact length rather than a standard category name. Anything threaded on one end only and plain on the other is technically a different fitting, sometimes called a half nipple or hex nipple depending on the shape of the unthreaded portion.
King Combination Nipples and Dual-Thread Designs
One specialized category worth understanding is the King Combination Nipple, also referred to in catalogs as a King nipple or combination nipple. A King Combination Nipple has two different thread types on each end, most commonly NPT (National Pipe Thread) on one side and a hose or garden thread on the other. This design solves a very specific problem: connecting a rigid pipe-threaded fitting directly to a hose, spray nozzle, or quick-connect coupling without requiring an additional adapter in between.
King Combination Nipples are widely used in agricultural irrigation, fire suppression equipment, pressure washing rigs, and portable water systems where a technician needs to switch quickly between a threaded pipe network and a hose-based attachment. Because the nipple itself bridges both thread standards, it removes one joint from the assembly, which lowers the number of potential leak points by roughly twenty to thirty percent in typical field installations compared with using two separate adapters.
| Nipple Style | Thread Pattern | Typical Use |
|---|---|---|
| Close Nipple | Fully threaded, no shoulder | Tight clearance joints |
| Shoulder Nipple | Threaded ends, plain center | General plumbing and HVAC |
| King Combination Nipple | NPT on one end, hose thread on other | Irrigation, pressure washing, hose connections |
| Long or Running Nipple | Threaded ends, extended length | Bridging wide gaps between fittings |
Common Materials Used for Pipe Nipples
Material choice determines how a nipple holds up against pressure, temperature, and the substance flowing through it. Selecting the wrong material is one of the most frequent causes of premature pipe joint failure.
- Galvanized steel: Resists corrosion in outdoor and water-line applications, commonly rated for pressures up to 150 psi at standard temperatures.
- Black steel: Preferred for gas lines and high-temperature steam systems where galvanizing is unnecessary or could flake under heat.
- Brass: Used where corrosion resistance and easier machining matter, frequently seen in King Combination Nipples for hose connections.
- Stainless steel: Selected for chemical processing, food-grade systems, and marine environments where rust resistance is critical.
- PVC and CPVC: Lightweight options for low-pressure water and irrigation lines where metal is unnecessary.
Brass nipples in particular dominate the combination nipple category because brass threads seal reliably against rubber washers found in standard garden hose fittings, something steel threads do not do as consistently without additional sealant.
How Pipe Nipple Sizes Are Measured
Nipple sizing follows two numbers: the pipe diameter (called the nominal pipe size, such as one-half inch or three-quarter inch) and the overall length measured from end to end, including the threaded portions. A nipple shorter than one and a half times its diameter is generally too short to thread safely into two fittings without the threads bottoming out.
For example, a half-inch nominal pipe nipple needs roughly three-quarters of an inch of thread engagement on each end to seal properly under code-recognized plumbing standards, which is why true close nipples in larger diameters are harder to find and often require custom cutting and threading rather than stock ordering.
- Measure the existing pipe or fitting diameter to confirm nominal pipe size.
- Measure the gap between the two fittings that need to be joined.
- Add the thread engagement depth required on each end to the gap measurement.
- Select the closest standard nipple length, rounding up rather than down.
Installation Tips That Prevent Leaks
Most leaks at a nipple joint trace back to one of three causes: insufficient thread sealant, over-tightening that cracks the fitting, or mismatched thread types being forced together. Applying pipe thread sealant or PTFE tape evenly around the male threads, working in the direction of the threading, reduces the chance of a thin spot that lets pressure escape.
When tightening, hand-threading the nipple until it stops turning freely, then adding roughly two to three additional turns with a wrench, is the standard approach used by licensed plumbers across most residential and light commercial work. Overtightening a close nipple is especially risky because there is no shoulder to absorb extra torque, and the thinner wall section in the center can crack under excessive force.
For King Combination Nipples specifically, checking that the hose-thread side has an intact rubber washer before connection is essential, since that washer, not the threads themselves, creates the watertight seal on the hose side of the joint.
Frequently Asked Questions About Pipe Nipples
What is the difference between a nipple and a coupling?
A coupling has female threads on both ends and is used to join two male-threaded pipes together, while a nipple has male threads on both ends and joins two female-threaded fittings. They serve opposite roles in the same connection.
Can a pipe nipple be cut to a custom length?
Yes, when a stock length is not available, a length of pipe can be cut and threaded on both ends to function as a custom nipple, provided the remaining wall thickness still meets the pressure rating needed for the application.
Why use a King Combination Nipple instead of a standard adapter?
A King Combination Nipple combines two thread types into a single piece, eliminating one connection point compared to using a separate pipe nipple plus a hose adapter, which reduces both material cost and the number of places a leak could start.
What thread sealant works best on metal nipples?
PTFE tape wrapped clockwise around the threads, or a pipe-rated thread sealant paste, both work reliably on steel and brass nipples; the choice often comes down to the temperature and chemical exposure the joint will face.
