What Is a Pipe Nipple? Types and Sizes

Quick Answer

A pipe nipple is a short length of pipe with male threads on both ends (TBE - threaded both ends) or one end (TOE - threaded one end). Nipples connect threaded fittings, valves, and instruments in small-bore piping systems. Standard sizes range from NPS 1/8 to NPS 4, with lengths from close nipple (fully threaded) to 12 inches or longer.

Pipe nipples are manufactured from standard pipe stock (typically Schedule 40 or 80) with NPT (National Pipe Taper) threads cut on the ends per ASME B1.20.1. They are one of the most common components in instrument connections, utility piping, and small-bore process piping.

Types of Pipe Nipples

Type	Description	Typical Use
Close nipple	Fully threaded, no unthreaded section	Minimum-length connection between two fittings
Short nipple	Short unthreaded section in the middle	Standard connections with slight spacing
Long nipple	Longer unthreaded section	Connections requiring specific spacing
Hex nipple	Hexagonal wrench flat in center	Easy installation/removal with wrench
Swage nipple	Reduces from one NPS to another	Size transition in threaded systems
Welding nipple	One end beveled for butt weld, one threaded	Transition from welded to threaded piping
Bull plug	One end threaded, other end closed	Dead-end closure

Standard Sizes

NPS	OD (mm)	Close Length (mm)	SCH 40 WT (mm)	SCH 80 WT (mm)
1/8	10.3	25	1.73	2.41
1/4	13.7	25	2.24	3.02
3/8	17.1	25	2.31	3.20
1/2	21.3	30	2.77	3.73
3/4	26.7	35	2.87	3.91
1	33.4	40	3.38	4.55
1-1/2	48.3	50	3.68	5.08
2	60.3	55	3.91	5.54
3	88.9	65	5.49	7.62
4	114.3	75	6.02	8.56

Standard nipple lengths: close, 1.5”, 2”, 2.5”, 3”, 4”, 5”, 6”, 8”, 10”, 12” (customary US sizes).

Materials

Material	ASTM Spec	Common Grades	Application
Carbon steel	A106 / A53	Gr. B	General-purpose process and utility
Stainless steel	A312 / A182	TP304, TP316	Corrosive service, instrumentation
Alloy steel	A335	P11, P22	High-temperature service
Brass	B43	C23000	Water systems, plumbing
Galvanized CS	A53 (galv.)	Gr. B	Utility water, fire protection

Swage Nipples

Swage nipples reduce from one pipe size to another within a single threaded fitting. They are available in concentric (centered) and eccentric (offset) configurations.

End Configuration	Description
TBE	Threaded both ends
BLE	Beveled large end, threaded small end
PBE	Plain both ends (no thread, no bevel)
BPE	Beveled one end, plain other end

Pro Tip

Never use close nipples where pipe stress, vibration, or thermal expansion is expected. The fully threaded body leaves no unthreaded wall section, making it the weakest nipple type. For instrument connections subject to vibration, use a minimum 3-inch nipple or switch to compression fittings with tubing.

Applications

• Instrument connections and gauge taps
• Utility piping (air, water, steam) in small bore sizes
• Drain and vent connections on process piping
• Pressure gauge and transmitter hook-ups
• Fire protection sprinkler systems (galvanized)
• Threaded branch connections on forged fittings

Read the full guide to pipe types