Difference between adapter, nipple and union

What is a Pipe Nipple

A pipe nipple is a length of straight pipe with male threads on both ends. It is one of the most popular category of pipe fittings. It is a connector or a coupling threaded on both ends. Pipe nipples are used to allow plumbing to be connected to a water heater or other plumbing. They are used to fit straight end hose or pipe. A combination of pipe nipples are recommended for low-pressure discharge and suction service for various compatible liquids and not for compressible products like air, nitrogen or steam.

The working pressure of pipe nipples will vary with the size and construction of the pipe, the type and number of clamps used, clamp placement, proper installation of clamps, temperature and product being conveyed. Pipe nipples are available in the widest variety of wall thicknesses and materials in the industry.

How to buy pipe nipples How to buy pipe unions How to buy adapters
Types of pipe nipples Types of pipe unions Types of Pipe Adapters
What is a Pipe Union What is a pipe adapter Difference between adapter, nipple and union

Materials used:
Various materials are used to make pipe nipples such as:
  • Brass
  • Aluminum
  • Stainless steel
  • Iron
  • Copper
  • PVC
  • Carbon steel
  • Cast Iron etc.

Pipe nipple fabrication:

  • Threaded nipples
  • Grooved nipples
  • Bended nipples
  • Barbed nipples
  • Seamless nipples

Finishes on pipe nipples:

  • Black coating
  • Electro galvanized
  • Hot-dipped galvanized finishes
  • Copper plating etc.

How to buy pipe nipples?

What should buyers look for in the bulk purchase of pipe nipples?
Tube selection

  • Material, thickness
  • Diameter

General technical specifications

  • Pressures
  • Safety coefficients
  • Temperatures
  • Conformity to the standards, Certifications
  • Standard, Double duty, Extra duty, Extra double duty

End Connections

  • Threads
  • Beveled Ends
  • Square Cut Ends
  • Grooved
  • Bended
  • Barbed
  • Seamless

Types of pipe nipples:

  • Barrel nipple: This is a type of a short tubular with a taper thread outside at each end and which is un-threaded in the middle.
  • Weld nipple: Weld nipple is used as another method of connecting tube fittings. These kind of nipples are suitable for use under extreme conditions of vibration, pressure surges and changes of temperature.
  • Swage nipple: The basic purpose of a swage nipple is to bringing the flow of fluids from one pipe size to another. These are available with plain, beveled or threaded ends.
  • Hexagon nipple: Hexagon nipples are available in a variety of threads, materials and lengths.

Pipe nipples: End finishes:

pipe nipples2 - Difference between adapter, nipple and union

Tapered pipe thread

pipe nipple3 - Difference between adapter, nipple and union

Straight pipe thread

pipe nipple4 - Difference between adapter, nipple and union

Roller Cut

pipe nipple5 - Difference between adapter, nipple and union

Reamed and chamfered

pipe nipple6 - Difference between adapter, nipple and union

Square cut

pipe nipple7 - Difference between adapter, nipple and union


Applications of pipe nipples:
Pipe nipples are used as pipe fittings in a wide variety of industrial applications like:

  • Chemical processing industries
  • Petrochemical
  • Pharmaceutical
  • Food & beverage
  • Pulp & paper
  • Shipbuilding / marine
  • Waste incineration
  • Machine building
  • Architectural
  • Semiconductor etc.

What is a Pipe Union

Pipe Union is a type of fitting equipment designed in such a way to unite two pipes which can be detached without causing any deformation to the pipes. Any kind of small diameter piping connections requiring a positive seal and easy assembly as well as disassembly are made with the help of pipe union. In other words, the pipe unions can disjoint two pipes very easily. They are widely demanded in the pipe fitting market.

Materials used:

  • Stainless steel
  • Cast iron
  • Aluminum
  • Nickel
  • Copper
  • Brass
  • Bronze
  • Alloy
  • Plastic
  • Rubber etc.

How to buy pipe unions?

Important features that buyers should look for:

  • Type
  • Standard
  • Material
  • Size
  • Durability
  • Easy to install
  • Corrosion resistance

Three parts of pipe union:

  • A nut
  • A female end
  • A male end

With the joining of the female and male ends, the nuts are used to provide the necessary pressure to seal the joint.
pipe union2 - Difference between adapter, nipple and unionThe parts of the pipe union are normally locked together by at least one radial screw or nut with sized cross section. When severe pulling stress is applied onto the pipe union from the outside, the locking screw breaks and removes the two parts of the union, which in turn separates together with the pipes to which they are attached. Under normal conditions elastically stressed sealing objects ensure maintenance of watertightness between the union parts.

Types of pipe unions:
There are two basic types of pipe unions:

  • Ground Joint Union
  • Flange Union

The difference between the two is that the former consists of three pieces while the latter two pieces.

pipe union3 - Difference between adapter, nipple and unionApplications of pipe unions:
Pipe unions are used in various municipal and industrial applications like as follows:

  • Fire protection
  • Process piping system
  • Water and wastewater etc.

Advantages of pipe union:
There are various advantages of pipe unions like:

  • To provide a leak-proof disconnection point in any piping system.
  • Used for inserting metering and regulating devices into any plumbing application.
  • Can connect piping system to vessels.
  • Can join two pipes of different size together.
  • Can easily remove the join between two pipes.
  • Easy to install.
  • Economical.

What is a pipe adapter?

Adapters are an extremely important pipe fitting that extend or terminate pipe runs. They are used to connect dissimilar pipes. These fittings are somewhat similar to pipe couplings, with the difference that they connect pipe of different types, one of which is an IPS (Iron Pipe Size).

Flex couplings sometime act like adapters. Pipe adapters may have either male or female IPS threads on one end and the opposite gender on the other end, which needs to be welded or soldered onto a smaller pipe. Adapters are used in a myriad of applications but they are typically used to connect different pipes to fixtures.

How to buy adapters?

Certain factors are to be taken into consideration like as follows:

  • Size is the most important parameter that has to be considered while selecting pipe adapters.
  • While going for straight threaded adapters, you should be certain that the compound used is compatible with system and environmental media.
  • The quality of the material used is also an important consideration while buying adapters for pipe.

Materials used:
High quality and durable materials are used for making pipe adapters. Some of the common materials include:

  • Steel
  • Cast Iron
  • Aluminum
  • Copper
  • Polymers
  • Rubber
  • Brass
  • Bronze etc.

Types of Pipe Adapters:
Adapters are available in various types and while different types of adapters are required for different applications. While buying adapters for pipe, the buyer should always select the right type for right application. Some of the common types of pipe adapter are:

locking pipe adapter - Difference between adapter, nipple and union

Locking Pipe Adapter:

These are special pipe adapters that are used to attach 6 inches pipe to drain basin of any size, which requires a straight-line connection.

offset pipe adapter - Difference between adapter, nipple and union

Offset Pipe Adapter:

These pipe adapters are used to attach 8 to 10 inches single wall pipe to 9 inches, 12 inches or 18 inches pipes used for drain basins and/or low profile drains, which require an offset connection.

male pipe adapter - Difference between adapter, nipple and union

Male Pipe Adapter:

Male pipe adapters are designed in such a way that they make minimum volume connection from the female pipe fittings on pressure gauges and regulators to dead volume internal fittings.

female pipe adapter - Difference between adapter, nipple and union

Female Pipe Adapter:

These pipe adapters make a minimum volume connection from the male pipe fittings, which are usually found in gas distribution plumbing to dead volume internal fittings.

Straight Thread Adapters:

These adapters are also referred as O-ring boss fittings and they are joined on the back of the male half of the connector against a locking surface of the female port. These adapters usually have straight threads, which do not seal and offer resistance for service pressure. Straight threaded adapters are again divided into two categories:straight thread adapters - Difference between adapter, nipple and union

  • Adjustable: As the name suggests, these adapters are adjustable and include fittings like elbows and tees. Adjustable straight threaded adapters help the user to change the shape in the direction as required, before they are tightened for assembling.
  • Non-adjustable: These fittings include plug or connector and they simply screw into a port and generally require no adjustment.

Uses of pipe adapters:
pipe adapters3 - Difference between adapter, nipple and unionSome important uses of pipe adapters are as follows:

  • Adapters are applicable in all sanitary pipes.
  • They are food grade rated.
  • They are insulated.
  • They are plated.
  • They provide high purity and excellent chemical resistance.
  • Leak-free designs in adapters can withstand high-pressure.
  • Adapters are ideal for high-vibration or side-load stressed applications.
  • They offer better flow rates.
  • They offer fewer potential leak points, thereby providing a seamless and convenient transition from piping to tubing systems.
  • In some cases, adapters eliminate the need for welded or threaded connections, which in turn save time and cost.

Difference between adapter , nipple and union

Union is a common pipe connection that can be easily installed and removed. Compared with coupling, it is easy to disassemble. As the name suggests, the union is active at both ends with a seal ring in the middle. It mainly consists of a nut, a cloud head, and a flat joint. It is a pipe joint machined by round bar or steel ingots. 
There are two connection forms for unions, i.e. socket welding and threaded connection. The socket welding is to insert the steel pipe into the socket to get welded. Therefore, it is called “plug-in union”. The threaded connection is to screw the steel pipe into the screw hole for connection. Besides, there are also external thread connections, called “threaded joint” and its main manufacturing standard is MSS SP-83. 
The union is widely used to connect pipes of different calibers, and is also widely used for connection of instruments, valves and pipes. It is mainly used in those sectors and fields that require high pressure and precision, such as petrochemical, medical and health, electric power, aerospace, military, fire, metallurgy, shipbuilding, gas, nuclear power, and environmental protection.
Nipple can be divided into single head and double head; it can also be divided into ordinary and hex nipples, both generally of equal diameter. It adopts either external thread or plug-in welding to reach the male/female head of the coupling/union, matching the seal. 
Nipples can also be divided into short tube, reducing nipple and threaded short nipple. Threaded short nipple is either single head threaded or double head threaded, commonly used in industrial pipe connections. The main thread standards are the American standard ASME B16.11 and the national standard GB/T14626. Among all, NPT (National-American Pipe Thread) RC threads (Conical Threaded, Female) enjoy great popularity in the market.
An adapter has different threads, sizes and/or type of fitting on each end. You would use a nipple to connect two 3/8 flare type hoses and you would use an adapter to connect a 3/8 flare fitting to a 1/2 inch pipe thread.

Source: Network Arrangement – China Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

Please notice that you might be interested in the other technical articles we’ve published:

  • What is a butt weld pipe fitting

  • The difference between pipe nipple and pipe coupling

  • What is a Pipe Nipple

  • What is a Pipe Union

  • What is a pipe thread

  • What is a Pipe Coupling

  • Development trend of high pressure pipe fittings


  1. https://www.yaang.com

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