pipe fitting

Pipe fitting work is done in many different trades: Plumbing, HVAC, Manufacturing, and many others. Pipe fitters (sometimes called simply "fitters") are represented in the USA by the United Association of Plumbers and Pipefitters.

Fitters work with a variety of pipe and tubing materials including several types of plastic, copper, steel, iron, aluminum, clay, and lead.

Steel Pipe

Steel pipe was once the most popular choice for supply of water and flammable gasses, but fell from favor as water pipe in the mid 20th century due to its tendency to rust. Steel pipe is still used in many homes and businesses to convey natural gas, and is a popular choice in fire sprinkler systems due to its high heat resistance.

Steel pipe is joined using thread connections, where tapered threads (See National Pipe Thread) are cut into the tubing section end, sealant is applied in the form of thread compound or PTFE tape (teflon tape) and it is then screwed into a threaded fitting using a pipe wrench.

Copper Tubing

Copper tubing is most often used for supply of hot and cold water, and as refrigerant line in HVAC systems. There are two basic types of copper tubing, soft copper and rigid copper. Copper tubing is joined using flare connection, compression connection, or sweat (solder). Copper offers a high level of resistance to corrosion, but is becoming very costly.

Soft Copper

Soft (or ductile) copper tubing can be bent easily to travel around obstacles in the path of the tubing. It can be joined by any of the three methods, and it is the only type of copper tubing suitable for flare connections. Soft copper is the most popular choice for refrigerant lines in split-system air conditioners and heat pumps.

Flare Connections

Flare connections require that the end of a tubing section be spread outward in a bell shape using a flare tool. A flare nut then compresses this bell-shaped end onto a male fitting. Flare connections are the most labor intensive of the three options, but are often the most reliable over the course of many years.

Rigid Copper

Rigid copper is a popular choice for water lines. It is joined using compression or sweat connection. Rigid copper cannot be bent and must use elbow fittings to go around corners or avoid obstacles.

Sweat Connections

Sweat fittings are smooth, and easily slip onto the end of a tubing section. The joint is then heated using a torch, and solder is melted into the connection. When the solder cools, it forms a very srong bond which can last for decades. Sweat connected rigid copper is the most popular choice for water supply lines in modern buildings. In situations such as new construction where many connections must be made at once, sweat offers much quicker reliable joinery than compression or flare.

Compression Connections

Compression fittings use a soft metal ring (the compression ring) which is squeezed onto the pipe and into the fitting by a compression nut. The soft metal conforms to the surface of the tubing and the fitting, and creates a seal. Compression connections do not typically have the long life that sweat connections offer, but are advantageous in many cases because they are easy to make using basic tools. A disadvantage in compression connections is that they take longer to make than sweat, and sometimes require retightening to avoid leaks.

Plastic Pipe

Plastic pipe is becoming a very popular choice for water supply and drain lines. It offers good durability, is low in cost, and easy to install.

PVC and CPVC

PVC is the most popular choice in plastic pipe. It is rigid, and uses thread or solvent weld (glue) connections. It is available in various pressure ratings, with the most common choice being Schedule 40 rated for 40 PSI of continuous pressure. Standard PVC can only be used for cold water supply, and is a very popular choice for drain line.

CPVC is the type of PVC that can be used for hot water supply.

PolyEthylene

Polyethylene or PE pipe is often used for the supply of hot and cold water. It can be joined using barb-fittings with clamp rings, or it can be heat-fused (sections can be melted together) using an appropriate tool. PE is usually black or gray in color, and is semi-flexible.

PE is a popular choice for underground loops in Geothermal heating, as supply line for lawn sprinkler systems, and is marketed under the trade names Qwest and QwestPEX for use in residential water supply.

ABS

ABS is recognizable by its rigidity and black color. It is used only for drainage lines and is lower in cost than PVC.

Nylon

Nylon tubing is often used for water lines inside appliances, and to convey various flammable fluids and solvents. It offers high resistance to chemical reaction.

Aluminum Tubing

Aluminum is sometimes used due to its low cost, resitance to corrosion and solvents, and for its ductility. Aluminum tube is more desirable than steel for the conveyance of flammable solvents, since it cannot create sparks when manipulated. Aluminum tubing can be connected by flare or compression fittings.

Occupational Hazards

Pipe fitters are often exposed to hazardous or dangerous materials, such as asbestos, lead, ammonia, steam, flammable gasses, various resins and solvents including benzine, and various refrigerants. Much progress was made in the 20th century toward eliminating hazardous materials. Many aspects of this are now regulated by law in most countries, including asbestos usage and removal, and refrigerant selection and handling; these being the result of many scientific discoveries in regard to the damage certain materials can cause to humans, animals, and the earth's ecological system.

See also:

Pipe