A fitting is used in pipe plumbing systems to connect straight pipe or tubing sections, to adapt to different

sizes or shapes, and for other purposes, such as regulating or measuringfluid flow. The term plumbing is
generally used to describe conveyance of water, gas, or liquid waste in ordinary domestic or commercial
environments, whereas piping is often used to describe high-performance (e.g. high pressure, high flow,
high temperature, hazardous materials) conveyance of fluids in specialized applications. The
term tubing is sometimes used for lighter-weight piping, especially types that are flexible enough to be
supplied in coiled form.

Fittings (especially uncommon types) require money, time, materials, and tools to install, so they are a
non-trivial part of piping and plumbing systems.[1] Valves are technically fittings, but are usually discussed
separately.

Contents

[hide]

 1 Standards

 2 Materials

 3 Gaskets

 4 Gender of fittings

 5 Common fittings for both piping and plumbing

o 5.1 Elbow

o 5.2 Coupling

o 5.3 Union

o 5.4 Reducer

o 5.5 Olets

o 5.6 Tee

o 5.7 Cross

o 5.8 Cap

o 5.9 Plug

o 5.10 Nipple

o 5.11 Barb

o 5.12 Valves

 6 Drain-waste-vent (DWV) and related fittings

o 6.1 Sweep elbow

o 6.2 Closet flange

o 6.3 Clean-outs

o 6.4 Trap primers

 o 6.5 Combo-tee

o 6.6 Sanitary tee

o 6.7 Double sanitary tee (sanitary cross)

o 6.8 Wye fitting

o 6.9 Double-tapped bushing

 7 Hydraulic fittings

 8 Connection methods

o 8.1 Fastener

o 8.2 Threaded pipe

o 8.3 Solvent welding

o 8.4 Soldering

o 8.5 Brazing

o 8.6 Welding

o 8.7 Compression fittings

o 8.8 Flare fittings

o 8.9 Flange fittings

o 8.10 Mechanical fittings

o 8.11 Grooved Pipe Fittings

o 8.12 Crimped or pressed fittings

 9 See also

 10 References

 11 External links
Standards[edit]
There are certain standard codes that need to be followed while designing or manufacturing any piping
system. Organizations that promulgate piping standards include:

 ASME - The American Society of Mechanical Engineers

 ASTM - American Society for Testing and Materials
 API - American Petroleum Institute
 AWS - American Welding Society
 AWWA - American Water Works Association
 MSS – Manufacturers' Standardization Society
 ANSI - American National Standards Institute
 NFPA - National Fire Protection Association
 EJMA - Expansion Joint Manufacturers Association
 CGA - Compressed Gas Association
For example pipes need to conform to the dimensional requirements of :

 ASME B36.10M - Welded and Seamless Wrought Steel Pipe

 ASME B36.19M - Stainless Steel Pipe
 ASME B31.3 2008 - Process Piping
The B31.3 code has requirements for piping found in petroleum refineries; chemical, pharmaceutical,
textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. This
code specifies requirements for materials and components, design, fabrication, assembly, erection,
examination, inspection, and testing of piping. This Code is applicable to piping for all fluids including: (1)
raw, intermediate, and finished chemicals; (2) petroleum products; (3) gas, steam, air and water; (4)
fluidized solids; (5) refrigerants; and (6) cryogenic fluids.

Materials[edit]
The material with which a pipe is manufactured often forms as the basis for choosing any pipe. Materials
that are used for manufacturing pipes include:

 Carbon Steel (CS)

 Low Temperature Service Carbon Steel (LTCS)
 Stainless Steel (SS)
 Malleable iron (malleable iron)
 Non-Ferrous Metals (Inconel, Incoloy, Cupro-nickel etc.)
 Non-Metallic (ABS, GRE, PVC, HDPE, tempered glass, etc. )
 Chrome-molybdenum steel (Alloy steel) — Generally used for high temperature service
The bodies of fittings for pipe and tubing are most often of the same base material as the pipe or tubing
being connected, for example,copper, steel, polyvinyl chloride (PVC), chlorinated polyvinyl
chloride (CPVC), or acrylonitrile butadiene styrene (ABS). However, any material that is allowed by the
plumbing, health, or building code (as applicable) may be used, but must be compatible with the other
materials in the system, the fluids being transported, and the temperatures and pressures inside and
outside of the system. For example, brass- or bronze-bodied fittings are common in otherwise copper
piping and plumbing systems. Fire hazards, earthquakeresistance, and other factors also influence choice
of fitting materials.

Gaskets[edit]
Gaskets are used for sealing of flange joints. In general, gaskets should not be reused.[citation needed]
[2]
Various types of gaskets are available depending upon their construction, materials, and features. The
following are the type of gaskets commonly used:

 Non-Metallic Gaskets (ASME B 16.21)

 Spiral-Wound Gaskets (ASME B 16.20)
 Ring Joint Gaskets (ASME B 16.20)
Non-Metallic Gaskets are used with flat face or raised face flanges. Spiral-Wound Gaskets are used with
raised face flanges. They are available with an inner ring and outer ring, which is also known as the
cantering ring. Ring Joint Gaskets are used with Ring Type Joint (RTJ) flanges. They are available in
octagonal or oval cross sections.

A very high surface stress is developed between an RTJ gasket and the flange groove when RTJ is
bolted up in a flange. This leads to plastic deformation of the gasket. Thus, the hardness of the gasket is
kept less than the hardness of the groove to achieve coining i.e. bringing two metal surfaces of different
hardness so tightly together that the softer surface deforms to match harder surface exactly in shape and
finish.[further explanation needed] Hence RTJ gaskets are recommended for reuse.[citation needed]

Gender of fittings[edit]
See also: Gender of connectors and fasteners

Piping or tubing are usually (but not always) inserted into fittings to make connections. To avoid
confusion, connections are conventionally assigned a gender of male or female, respectively abbreviated
as "M" or "F". An example of this is a "3/4 inch female adapter NPT," which would have a corresponding
male connection of the same size and thread standard (in this case, NPT).

Common fittings for both piping and plumbing[edit]

While there are hundreds of specialized fittings manufactured, some common types of fittings are used
widely in piping and plumbing systems.

Elbow[edit]
See also: Street elbow

Short radius or regular 45° elbow (copper sweat)

Long radius or sweep 90° elbow (copper sweat)

An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction,
usually a 90° or 45° angle, though 22.5° elbows are also made. The ends may be machined for butt
welding, threaded (usually female), or socketed, etc. When the two ends differ in size, the fitting is called
a reducing elbow or reducer elbow.

Elbows are categorized based on various design features as below:

 Long Radius (LR) Elbows – radius is 1.5 times the pipe diameter
 Short Radius (SR) Elbows – radius is 1.0 times the pipe diameter
 90 Degree Elbow – where change in direction required is 90°
 45 Degree Elbow – where change in direction required is 45°
A 90 degree elbow is also called a "90 bend" or "90 ell". It is a fitting which is bent in such a way to
produce 90 degree change in the direction of flow in the pipe. It is used to change the direction in piping
and is also sometimes called a "quarter bend". A 90 degree elbow attaches readily to plastic, copper, cast
iron, steel and lead. It can also attach to rubber with stainless steel clamps. It is available in many
materials like silicone, rubber compounds, galvanized steel, etc. The main application of an elbow (90
degree) is to connect hoses to valves, water pressure pumps, and deck drains. These elbows can be
made from tough nylon material or NPT thread.

A 45 degree elbow is also called a "45 bend" or "45 ell". It is commonly used in water supply facilities,
food industrial pipeline networks, chemical industrial pipeline networks, electronic industrial pipeline
networks, air conditioning facility pipeline, agriculture and garden production transporting system, pipeline
network for solar energy facility, etc.

Most elbows are available in short radius or long radius variants. The short radius elbows have a center-
to-end distance equal to the Nominal Pipe Size (NPS) in inches, while the long radius is 1.5 times the
NPS in inches. Short elbows are widely available, and are typically used in pressurized systems.

Long elbows are typically used in low-pressure gravity-fed systems and other applications where low
turbulence and minimum deposition of entrained solids are of concern. They are readily available
in acrylonitrile butadiene styrene (ABS plastic), polyvinyl chloride (PVC) for DWV, sewage and central
vacuums, chlorinated polyvinyl chloride (CPVC) and copper for 1950s to 1960s houses with copper
drains.

Coupling[edit]

Pipe coupling (copper sweat)

A coupling connects two pipes to each other. If the size of the pipe is not the same, the fitting may be
called a reducing coupling or reducer, or an adapter. By convention, the term "expander" is not
generally used for a coupler that increases pipe size; instead the term "reducer" is used.

Union[edit]

A combination pipe union and reducer fitting (brass threaded)

A union is similar to a coupling, except it is designed to allow quick and convenient disconnection of pipes
for maintenance or fixture replacement. While a coupling would require either solvent
welding, soldering or being able to rotate with all the pipes adjacent as with a threaded coupling, a union
provides a simple transition, allowing easy connection or disconnection at any future time. A standard
union pipe is made in three parts consisting of a nut, a female end, and a male end. When the female and
male ends are joined, the nuts then provide the necessary pressure to seal the joint. Since the mating
ends of the union are interchangeable, changing of a valve or other device can be achieved with a
minimum loss of time. Pipe unions are essentially a type of flange connector, as discussed further below.

In addition to standard, simple unions, other types of union exist:

 Dielectric unions are unions with dielectric insulation, used to separate dissimilar metals (such as
copper and galvanized steel) to avoid the damaging effects of galvanic corrosion. When two
dissimilar metals are in contact with an electrically conductive solution (even tap water is conductive),
they will form a battery and generate a voltage byelectrolysis. When the two metals are in direct
 contact with each other, the electric current from one metal to the other will cause a movement of
ions from one to the other, dissolving one metal and depositing it on the other. A dielectric union
breaks the electric current path with a plastic liner between two halves of the union, thus limiting
galvanic corrosion.
 Rotary unions are unions that allow for rotation of one of the united parts.

Reducer[edit]

Reducer fittings, bronze threaded (left) and copper sweat (right)

Main article: Reducer

A reducer allows for a change in pipe size to meet hydraulic flow requirements of the system, or to adapt
to existing piping of a different size. Reducers are usually concentric buteccentric reducers are used when
required to maintain the same top- or bottom-of-pipe level.

Olets[edit]
Whenever branch connections are required in size where reducing tees are not available and/or when the
branch connections are of smaller size as compared to header size, olets are generally used[further explanation
needed]
. The following are few configurations of olet connections :

 Flanged Olet
 Socket-Weld & Threaded Olet
 Lateral & Elbow Olets
 Nipple Olet
 Butt-Weld Olet
 Swage Nipples
Tee[edit]
Pipe tee (copper sweat)

A tee is the most common pipe fitting. It is available with all female thread sockets, all solvent weld
sockets, or with opposed solvent weld sockets and a side outlet with female threads. It is used to either
combine or split a fluid flow. It is a type of pipe fitting which is T-shaped having two outlets, at 90° to the
connection to the main line. It is a short piece of pipe with a lateral outlet. A tee is used for connecting
pipes of different diameters or for changing the direction of pipe runs. They are made of various materials
and available in various sizes and finishes. They are extensively used in pipeline networks to transport
two-phase fluid mixtures. They are categorized as:

 Equal
 Unequal
When the size of the branch is same as header pipes, equal tee is used and when the branch size is less
than that of header size, reduced tee will be used. Most common are tees with the same inlet and outlet
sizes. Some of the industrial tees are Straight Tee, Reducing Tee, Double Branch Tee, Double Branch
Reducing Tee, Conical Tee, Double Branch Conical Tee, Bullhead Tee, Conical Reducing Tee, Double
Branch Conical Reducing Tee, Tangential Tee, and Double Branch Tangential Tee.

The above tees are categorized on the basis of their shapes and structure. They can also be classified on
the basis of the application they are required to perform.[further explanation needed]

The three outlet sizes should be named in order (e.g. left, middle, right; measuring 15-22-15).[further explanation
needed]

The three sizes of a tee are end x end x center. So if you want a tee that is 1" on both ends and 3/4" in
the center it would be 1" x 1" x 3/4".

Cross[edit]
Cross fittings are also called 4-way fittings. If a branch line passes completely through a tee, the fitting
becomes a cross. A cross has one inlet and three outlets, or vice versa. They often have solvent welded
socket ends or female threaded ends.

Cross fittings can generate a huge amount of stress on pipe as temperature changes, because they are
at the center of four connection points. A tee is more steady than a cross, as a tee behaves like a three-
legged stool, while a cross behaves like a four-legged stool. (Geometrically, "any 3 non-colinear points
define a plane" thus 3 legs are inherently stable.) Crosses are common in fire sprinklersystems,[why?] but
not in plumbing, due to their extra cost as compared to using two tees.

Cap[edit]
Pipe cap (copper sweat)

A type of pipe fitting, usually liquid or gas tight, which covers the end of a pipe. A cap is used like plug,
except that the pipe cap screws or attaches on the male thread of a pipe. A cap may have a solvent weld
socket end or a female threaded end and the other end closed off. In plumbing systems that use threads,
the cap has female threads. Industrial caps can be round, square, rectangular, U-shaped, I-shaped and
may have a round hand grip or a flat hand grip.

If a solvent weld cap is used to provide for a future connection point, several inches of pipe must be left
before the cap. This is because when the cap is cut off for the future connection, enough pipe must
remain to allow a new fitting to be glued onto it.

Plug[edit]
A plug closes off the end of a pipe. It is similar to a cap but it fits inside the fitting it is mated to. In a
threaded iron pipe plumbing system, plugs have male threads. Some of the popular types of plugs are:

 Mechanical pipe plug

 Pneumatic disk pipe plug
 Single size pneumatic all rubber pipe plug
 Multi-size pneumatic pipe plug
 Multi-size flow-through pipe plug
 High pressure pipe plug
Nipple[edit]
Main article: Nipple (plumbing)

A short stub of pipe, usually threaded steel, brass, chlorinated polyvinyl chloride (CPVC) or copper;
occasionally just bare copper. A nipple is defined as being a short stub of pipe which has external male
pipe threads at each end, for connecting two other fittings. Nipples are commonly used for plumbing and
hoses, and second as valves for funnels and pipes.[clarification needed]

Barb[edit]
A plastic elbow fitting with a hose barb at the top, and male pipe threads at the bottom

A barb is used to connect flexible hoses to pipes. A barb clamp fitting has a male-threaded end used to
mate with the female threads. The other end of the fitting has either a single or multiple barbed tube
having a tapered stub with ridges, which is inserted into the flexible hose to secure it. An adjustable worm
drive screw clamp helps to keep the hose from slipping off the barbed tube. Barb fittings can be made of
plastic or brass. Brass is used for hot water applications while plastic is used for cold. The barb fitting can
be either elbow-shaped or straight.

Valves[edit]
Main article: Valve

Valves are equipment designed to stop or regulate flow of any fluid (liquid, gas, condensate, stem, slurry,
etc.) in its path. Valves are categorized depending on their applications like isolation, throttling, and non-
return. Various type of valves are available depending upon the type of construction as follows:

 Gate valve - used for isolation only

 Plug valve - used for isolation only
 Globe valve - used for throttling
 Butterfly valve - used for isolation as well as throttling
 Check valve - used for preventing reverse flow (non-return)
 Diaphragm valve - used for isolation as well as throttling
 Ball valve - used for isolation only
Drain-waste-vent (DWV) and related fittings[edit]
Because they operate at low pressure and rely on gravity to move fluids (and often entrained
solids), drain-waste-vent systems use fittings designed to be as smooth as possible on their interior
surfaces. The fittings may be "belled" or expanded slightly in diameter, or otherwise shaped to
accommodate insertion of pipe or tubing, without forming a sharp interior ridge that might catch debris or
accumulate buildup of material and cause clogging.[3] The absence of interior snags also makes it much
easier to "snake out" or "rod out" a clogged pipe using long flexible tools made for this purpose.

Underground piping systems for landscaping drainage, or disposal of stormwater or groundwater,

similarly use gravity flow at low pressure, often with entrained solids. Piping fittings used for these
systems bear a strong resemblance to DWV fittings, though often at a larger scale.[4] When high peak flow
volumes are involved, the design and construction of these systems are closely inter-related
tosewer design.

Fittings for central vacuum systems are very similar to DWV fittings, though usually of thinner and lighter
construction, since the weight of the materials conveyed through the system is much less. Vacuum
system designs share with DWV designs a concern about eliminating internal ridges, burrs, sharp turns,
or other obstructions to smooth flow that might cause build-up of material into pipe blockages.

Sweep elbow[edit]
DWV elbows are usually long radius or sweep types, to reduce flow resistance and solids deposition
when the direction of flow is changed. A well-designed system will often employ multiple 45° elbows in
preference over 90° elbows (even sweep elbows), to reduce flow disruption as much as possible.

Central vacuum system inlet fittings are intentionally designed with a tighter radius of curvature than any
other bends in the system. This is done to ensure that if any vacuumed debris becomes stuck, it will jam
right at the inlet, where it is easiest to discover and to remove.

Closet flange[edit]
The closet flange is the drain pipe flange to which a water closet (toilet) is attached. It is a specialized
type of flange connection designed to sit flush with the floor, allowing a standard toilet to be installed
above it.

Clean-outs[edit]
Clean-outs are fittings with removable elements that allow access to drains without requiring removal of
plumbing fixtures. They are used for allowing an auger or plumber's snake to clean out a plugged drain.
Clean-outs should be placed in accessible locations at regular intervals throughout a drainage system,
often including outside the building, because clean-out augers have limited length. The minimum
requirement is typically at the end of each branch in piping, just ahead of each water closet, at the base of
each vertical stack, and both inside and outside the building in the building main drain/sewer. Clean-outs
normally have screw-on caps or screw-in plugs. Clean-outs are also known as rodding eyes from the
eye-shaped cover plates often used on external versions.

Trap primers[edit]
Trap primers regularly inject water into traps so that "water seals" are maintained, as necessary to
keep sewer gases out of buildings. The trap primer must be installed in a readily available place for easy
access for adjustments, replacement, and repair. Strictly speaking, a trap primer is a specialized valve,
and it is usually connected to a clean water supply, in addition to a DWV system.[5]Because of this dual
connection, the design usually must be certified to resist accidental backflow of contaminated water.

Combo-tee[edit]
A combination tee (combo tee) is a tee with a gradually curving center connecting joint. It is used in drain
systems to provide a smooth, gradually curving path to reduce the likelihood of clogs, and to ease
pushing a plumber's snake through a drain system. The "combo" is a combination of a wye and a 1/8
bend or 45° elbow.

Sanitary tee[edit]
A sanitary tee is a tee with a curved center section. In drainage systems it is primarily used to connect
horizontal drains ( including fixture trap arms) to vertical drains. (It is against all major codes to use a
sanitary tee to connect a vertical drain to a horizontal drain.) The center connection is generally
connected to the pipe which leads to a trap (the trap arm).

Double sanitary tee (sanitary cross)[edit]

Similar to a cross. This fitting differs from a standard cross in that two of the ports have curved inlets. The
fitting has been used in the past for connecting the drains of back-to-back fixtures (such as back-to-back
bathroom sinks). Some current codes (including the 2006 UPC) prohibit the use of this fitting for that
purpose, instead requiring a special "double fixture fitting".[further explanation needed]

Wye fitting[edit]
A fitting with three openings, a wye is used to create branch lines. It is a type of waste fitting tee which
has the side inlet pipe entering at a 45° angle, or an angle other than 90 degrees. A standard wye is a "Y"
shaped fitting which allows one pipe to be joined to another at a 45 degree angle.

Wyes are similar to tees except that the branch line is angled to reduce friction and turbulence that could
hamper the flow. The connection is typically at a 45-degree angle rather than a 90-degree angle. If a
branch turns out further at the end to be perpendicular to the through line, the fitting becomes a "tee wye"
(TY).

PVDF Corrosive Waste Piping Systems utilize wye fittings that feature a smooth inside diameter without
any irregularities, for uninterrupted flow path. These fittings should be able to withstand acids, bases, and
solvents. Flame-retardant systems withstand intermittent corrosive fluids up to high temperatures.
Polypropylene and PVDF Double Wyes and Double Reducing Wyes come in various sizes and are
largely used for this purpose.

A wye branch allows splitting a branch line equally in two directions. The opening sizes can vary for
different situations, for instance in situation where a large main line needs to be split into two smaller
branches.

Low-priced wyes are often spot-welded together, whereas industrial wyes have a continuous weld at each
seam. In long-distance pipeline applications, a true Wye fitting is also engineered for closed system
instrumentation pigging configurations or wherever a smooth pipe branch is required.

Double-tapped bushing[edit]
A double-tapped bushing is a fitting that has opposing threads on the inside diameter of the bushing.

Hydraulic fittings[edit]
See also: Hydraulic machinery

Hydraulic systems use extremely high fluid pressures to create useful work, such as in the hydraulic
actuators for powered machinery such as bulldozers and backhoes. Therefore, hydraulic fittings are
designed and rated for much greater pressures than those experienced in general piping systems, and
they are generally not compatible for use in general plumbing. Hydraulic fittings are designed and
constructed to resist high pressure leakage and sudden explosive failure. More information on hydraulics
and their specialized fittings can be found in the hydraulic machinery article.
Connection methods[edit]
Much of the work of installing a piping or plumbing system involves making leakproof, reliable
connections. In addition, most piping requires mechanical support against gravity and other forces (such
as wind loads and earthquakes) that might disrupt an installation.[6]Depending on the connection
technology used, basic skills may be sufficient, or specialized skills and professional licensure may be
required.

Fastener[edit]
A fastener is a hardware device that mechanically joins or affixes two or more objects together. They are
usually used to attach pipe and fittings to mechanical supports in buildings, but not to interconnect the
actual pipes to each other. The following are the type of fasteners commonly used with piping:

 Stud bolt with nut — Usually the stud bolts are used with full threading and with two heavy hexagonal
nuts.
 Machine bolt with nut
 Powder-actuated tool (PAT) fastener — Usually a simple nail, or a threaded stud, driven into concrete
or masonry
Threaded pipe[edit]

MIP pipe and FIP elbow fitting (steel threaded)

A threaded pipe is a pipe with a screw thread at one or both ends for assembly. Steel pipe is often joined
using threaded connections, where tapered threads (in the US/Canada seeNational Pipe Thread, in
Commonwealth Nations such as the UK, Australia, New Zealand see British standard pipe thread) are cut
into the end of the tubing segment, sealant is applied in the form of thread sealing compound or thread
seal tape (also known as PTFE orTeflon tape), and it is then threaded into a corresponding threaded
fitting using a pipe wrench.

Threaded steel pipe is still widely used in many homes and businesses to convey natural
gas or propane fuel, and is a popular choice in fire sprinkler systems due to its high heat resistance.
Threaded brass pipe was once used in a similar fashion, and was considered superior to steel for carrying
drinking water, but is now effectively obsolete.

Assembling threaded steel pipe takes some skill, plus careful planning to allow lengths of pipe to be
screwed together in proper sequence. Most threaded pipe systems require occasional use of pipe union
fittings to allow final assembly.

Solvent welding[edit]
A solvent is applied to PVC, CPVC, ABS, or other plastic piping, to partially dissolve and fuse the
adjacent surfaces of piping and fitting. Solvent welding is usually used with a sleeve-type joint, to connect
pipe and fittings made of the same (or closely compatible) material.

Unlike regular welding of metals, solvent welding is relatively easy to perform, although care is still
needed to produce reliable joints. Solvents typically used for plastics are usually toxic, may
be carcinogenic, and may also be flammable, requiring adequate ventilation.

Soldering[edit]
To make a solder connection, a chemical flux is applied to the inner sleeve of a sleeve type joint, and the
pipe is inserted. The joint is then heated using a propane torch or MAPP gas torch, solder is applied to
the heated joint, and the melted solder is drawn into the joint by capillary action as the flux
vaporizes. Sweating is an alternate term sometimes used to describe soldering of pipe joints.

In situations where many connections must be made in a short period of time (such as plumbing of a new
building), solder offers much quicker and much less expensive joinery than compression or flare fittings. A
degree of skill is needed to rapidly make large numbers of reliable soldered joints. If flux residues are
thoroughly cleaned, soldering can produce a long-lasting connection at low cost. However, the use of
open flames for heating joints can present fire and health hazards to occupants of a building being
worked on, and requires adequate ventilation.

Brazing[edit]
Brazing is a thermal joining process in which the two pieces of the base metal are joined when a molten
brazing filler metal is allowed to be drawn into a capillary gap between them. It is used to join most metals
and alloys commonly used in engineering. Brazing filler metals have very high melting points, but always
below the melting point of the metals being joined. It is closely related to soldering, but uses harder
materials and higher temperatures. Brazing can be used to join pipes, rods, metal pieces or any other
shape as long as the pieces fit neatly against each other without leaving large gaps. It is also capable of
joining tungsten carbide, ceramics and similar non-metallic materials.

Successfully brazed joints are as strong as the parent metal pieces being joined and can withstand
demanding service conditions i.e. they are strong and ductile. Well brazed joints have smooth, neat fillets
and they offer good electrical conductivity.

Welding[edit]
Welding of metals differs from soldering and brazing, in that the connection is made without adding a
special low-melting-point material (e.g. solder) to complete a joint. Instead, the material of the pipe or
tubing is itself partially melted in a carefully controlled manner, and the fitting and piping are directly fused
together. Generally this requires that the piping and the fitting be made of the same (or closely
compatible) material. Pipe welding is a specialized skill, and is often performed by specially licensed
workers who are tested periodically for the quality of their work. For critical applications, every joint is
tested using non-destructive testing methods.
Properly welded and inspected joints are considered to be very reliable, robust, and long-lasting. Proper
ventilation is essential to remove dangerous metallic fumes from welding operations. Because of the
expensive skilled labor required, welded pipe joints are usually restricted to high-performance
applications, such as in shipbuilding, chemical reactors, and nuclear reactors.

Compression fittings[edit]

Compression connectors on an isolating valve. The red metal is a copper compression ring.

Main article: Compression fitting

Compression fittings consist of a tapered concave conical seat, a hollow barrel-shaped compression ring
(sometimes called a ferrule), and a compression nut which is threaded onto the body of the fitting and
tightened to make a leakproof connection. Fittings are typically made of brass or plastic, but stainless
steel or other materials may be used.

Compression connections do not typically have the long life that sweat connections offer, but are
advantageous in many cases because they are easy to install using basic tools. A disadvantage of
compression connections is that they take longer to make than sweated joints, and sometimes require
retightening over time to stop leaks.

Flare fittings[edit]

Flare connection: 1 Screw thread, 2 O-ring, 3 Body, 4 Nut, 5 Seal interface, 6 Support ring (sleeve), 7 Flared tubing.

Flared connectors should not be confused with compression connectors, with which they are generally
not interchangeable. Flared connectors lack a compression ring, but do use a threaded nut. A special
flaring tool is used to enlarge tubing into a tapered "bellmouth" shape that matches the tapered projecting
conical shape of the flare fitting. The flare nut, which has previously been installed over the tubing, is then
tightened onto the fitting. Fittings are typically made of brass or plastic, but stainless steel or other
materials may be used.
Flare connections are a labor-intensive method of making connections, but are quite reliable over the
course of many years. Flared fittings are sometimes thought to be more secure against leaks and sudden
failures, and are often preferred for safety-critical connections, such as in hydraulic brake systems.

Flange fittings[edit]

Flange connection, using a gasket

Flanges are generally used when there is a connection to valves, in-line instruments and/or connection to
equipment nozzles is required. Flange fittings generally involve pressing two surfaces to be joined tightly
together, by means of threaded bolts, wedges, clamps, or other means of applying
high compressive forces.[7] Often, a gasket, packing, or an O-ring is installed between the flanges to
prevent leakage, but it is sometimes possible to use only a special grease, or nothing at all, if the mating
surfaces are precisely formed. Flanges are designed to the following pressure ratings: 150 lb, 300 lb,
400 lb, 600 lb, 900 lb,1500 lb and 2500 lb or 10 Bar, 15Bar, 25Bar, 40Bar, 64Bar, 100Bar and 150Bar.
Various types of flanges are available depending upon the type of their constructional features. The
following are types of flanges generally used in piping. These flanges are available with different facing
like raised face, flat face, ring joint face etc.

 Orifice
 Threaded
 Slip-On
 Blind
 Weld Neck
 Socket
 Lap Joint
 Reducing
Slip On flanges are slipped over the pipe and then welded from both inside and outside to provide
sufficient strength and prevent leakage. This flange is used instead of weld necks by many users because
of its lower cost and also the fact that it requires less accuracy when cutting pipe to length.

Blind flanges do not have a bore and are used to shut off a piping system or vassal opening. Its design
permits easy access to vassal or piping system for inspection purpose. It can be supplied with or without
hubs at the manufacturer's option.
Weld Neck Flanges are designed to be joined to a piping system by butt welding. They are expensive
because of its long neck, but is preferred for high stresses to the pipe, reducing stress applications. The
neck, or hub, transmits stress concentration at the base of the flange. The gradual transition of thickness
from the base of the hub to the wall thickness at the butt weld provides important reinforcement of the
flange. Turbulence and erosion are reduced due to the matching bore size of the pipe and flange.

Socket Flanges are similar to a slip on flanges in outline, but the bore is counter-bored to accept pipe.
The diameter of the remaining bore is same as the inside diameter of the pipe. A fillet weld around the
hub of the flange attaches the flange to the pipe. An optional interval weld may be applied in high stress
applications. Its biggest use is in high pressure system such as hydraulic and steam lines.

Lap Joint flange is again similar to a slip flange, but it has radius at the intersection of the bore and the
flange face to accommodate a lap stub end. The face on the stub end forms the gasket face of the flange.
Its applications are where sections of piping systems need to be dismantled quickly and easily for
inspection or replacement.

Flanged connections tend to be more bulky than other connections, but can perform well in demanding
applications, such as largewater mains and hydroelectric power systems.

Multiple mechanical sleeve clamps connecting piping

Mechanical fittings[edit]
Manufacturers such as Victaulic or Grinnell produce special sleeve clamp fittings that are increasingly
replacing classic flanged connections. They typically attach to the end of a pipe segment by using
circumferential grooves pressed (or cut, in older designs) around the end of the pipe to be joined.
Mechanical connectors are widely used on larger steel pipes, but can also be used with other materials.

The chief advantage of these newer connectors is that they can be installed in the field after cutting the
pipe to length, which is much faster than traditional flanged connections, which must be factory-welded or
field-welded to pipe segments.

Grooved Pipe Fittings[edit]

A variation of mechanical fittings are grooved fittings such as Victaulic grooved fittings. This “grooved”
concept, or grooved pipe joining system, first available in 1925, uses a mechanical coupling, also named
mechanical fitting combined with grooved pipe ends to join piping systems. A grooved fitting, also called a
grooved coupling, has four elements:

 the groove pipe

 the gasket
 coupling housing
 the nuts and bolts
The groove is made by cold forming or machining a groove into the end of a pipe. A gasket encompassed
by the coupling housing is wrapped around the two pipe ends, and the key sections of the coupling
housing engage the grooves. The bolts and nuts are tightened with a socket wrench or impact wrench. In
the installed state, the coupling housing encases the gasket and engages the grooves around the
circumference of the pipe to create a leak-tight seal in a self-restrained pipe joint.

There are two basic grooved coupling styles:

 Flexible grooved couplings- allow a limited amount of angular movement

 Rigid grooved couplings- do not allow movement and can be used wherever immobility in the pipe
joint is needed, similar to a flanged or welded joint.

Fittings for crimping

Crimped or pressed fittings[edit]

Crimped or pressed connections use special fittings which are permanently attached to tubing with a
powered crimper. The special fittings, manufactured with sealant already inside, slide over the tubing to
be connected. High pressure is used to deform the fitting and compress the sealant against the inner
tubing, creating a leakproof seal.

The advantages of this method are that it should last as long as the tubing, it takes less time to complete
than other methods, it is cleaner in both appearance and the materials used to make the connection, and
no open flame is used during the connection process. The disadvantages are that the fittings used are
harder to find and cost significantly more than sweat type fittings.

See also[edit]
 Flange
 Gladhand connector
 Pipe fitting
 Plumber
 Rainwater, surface, and subsurface water drainage
 Septic systems
 Traps, Drains, and Vents
 Water cooling
 Water supply systems
How to Recognize Different Types of Pipes
By Donald R. Prestly from Plumbing Do-It-Yourself For Dummies

To tackle a do-it-yourself plumbing project, you need to know how to recognize different types of pipes. Recognizing
the different types of pipes within your house is vital to knowing the right repair technique.

The most common pipes used today are copper, PVC, or ABS. However, when dealing with older homes, you might
encounter a number of other piping material. For example, homes built before 1960 used galvanized steel or cast iron
DWV (drain/waste/vent) pipe systems.

Here’s a quick look at types of pipes commonly used in homes, beginning with the pipes used for DWV systems.

 Cast iron: Commonly used before 1960 for the vertical drain, vent stacks, and sometimes the horizontal drain
lines. Cast iron is durable, but can rust over time. Call a professional plumber to replace rusted sections with
plastic (PVC or ABS) and the correct transition fittings.
 Plastic: Plastic pipe comes as either ABS (acrylonitrile-butadiene-styrene) or PVC (polyvinyl-chloride). Most
homes since mid-1970 have plastic pipes and fittings because it’s inexpensive and easy to use. Simply glue the
joints using a primer and liquid cement.

 ABS: This black pipe was the first plastic pipe to be used in residential plumbing. Today, many areas don’t
allow ABS in new construction because joints can come loose. Check with your local plumbing inspector if
you want to use ABS.
 PVC: This white or cream-colored pipe is the most commonly used pipe for drain lines. It’s strong,
untouchable by chemicals, and seems to last forever! The rating and diameter is stamped right on the pipe.
 Schedule 40 PVC is strong enough for residential drain lines, but check with your plumbing inspector
first. CPVC (chlorinated polyvinyl chloride) pipe has the strength of PVC but is heat-resistant, which makes
it acceptable in many regions for use on interior supply lines.Schedule 80 PVC is sometimes used for cold-
water supply lines, but it isn’t allowed in some regions because it isn’t suitable for hot water.
 Do-it-yourselfers can handle ABS or PVC pipes, but call a professional for cast iron.

 PEX: PEX (cross-linked polyethylene) is the newest pipe for residential use. Approved in many regions of the
country, PEX is easy to install because it cuts easily, is flexible, and usescompression fittings. However, more
permanent connections require a special crimping tool. PEX is three to four times more expensive than copper
or plastic.
 Steel: Galvanized steel pipe is common in older homes. Galvanized pipe is strong, but lasts only about 50
years. Before repairing, consider replacing instead. Call a professional to deal with it.
 Copper: Copper pipe is resists corrosion, so it’s commonly used pipe in water supply lines. It costs more than
plastic but it lasts! There are two common types of copper pipe:
 Rigid copper, which comes in three thicknesses. Type M is the thinnest but is strong enough for most
homes. Types L and Type K are thicker and used in outdoor and drain applications. To cut rigid copper,
you'll need a wheel cutter, tube cutter, or a hacksaw. Pipes are usually connected
with soldered (sweat) fittings and compression fittings can connect the pipe to shut-off valves.
 Flexible copper, which is often used for dishwashers, refrigerator icemakers, and other appliances that
need a water supply. It’s easy to bend, but if it kinks, you must cut the piece off and replace it. Sections of
flexible copper pipe are joined using either soldered or compression fittings.

Consider longevity and expense when choosing piping.