How to choose the right pipe fitting?

What are pipe fittings?

Pipe fittings, also known as pipe connectors, are used to connect one pipe to another to extend the length of a piping system or change the direction of flow in a piping system. These fittings are used to combine, divert, or reduce the flow of water supply. They come in a variety of sizes to fit the pipes they connect to.

Types of pipe fittings materials

Stainless Steel

Stainless steel is a popular choice for pipe fittings due to its excellent corrosion resistance, strength, and aesthetics. It is commonly used in industries where hygiene and corrosion resistance are critical, such as food processing, pharmaceuticals, and chemicals.

Carbon Steel

Carbon steel is another common metal material used for pipe fittings. It is known for its strength and affordability, making it suitable for many industrial applications. Carbon steel fittings are commonly used in construction, oil and gas, and water supply systems.

Brass

Brass is an alloy of copper and zinc that has good corrosion resistance and workability. It is commonly used in fittings for residential and commercial plumbing systems.

PVC (Polyvinyl Chloride)

PVC is a plastic commonly used in pipe fittings for water and sewer systems. It is lightweight, durable, resistant to corrosion and chemicals. PVC fitting material is ideal for a variety of applications due to its affordability and performance.

CPVC (Chlorinated Polyvinyl Chloride)

CPVC is a modified form of PVC that can withstand higher temperatures. It is commonly used in hot water systems and applications requiring higher temperature resistance.

PEX (Cross-Linked Polyethylene)

PEX is a flexible plastic material used for pipe fittings in water systems. It is known for its flexibility, ease of installation, and frost resistance.

Types of pipe fittings and their purposes

There are many types of fittings used in plumbing systems, but some are used more frequently. Below we have listed some of the most popular types of fittings.

Tee: A tee fitting contains one inlet and two outlets, one at a 90-degree angle and the other at a 180-degree angle. Tee fittings get their name from their resemblance to the letter “T.” These fittings are one of the most common types of fittings found in piping systems. This is because tee fittings are versatile and easy to manufacture. Tee fittings can be used to divert, combine, or redirect flow in a plumbing system.

Used for: Connecting and diverting flow through two or three pipes.

Coupling: A coupling is used to connect two pipes from the outside of the pipe. Couplings are usually installed as a permanent connection between pipes of the same size or different sizes. Couplings that connect two pipes of different sizes is called a reducers and couplings that connect two pipes of different standards is called an adapters.

Used for: Connecting two pipes from the outside

Adapters: Adapter fittings are used when the two pipes to be connected do not have the same connection standard or size. For example, one pipe may require BSP fittings, while another pipe may contain NPT threads. In this case, a BSP to NPT adapter with appropriate dimensions is required at both ends. An adapter that joins two pipes of different sizes is called a reducing coupling. These couplings reduce the flow area between two pipes without changing their diameter.

Used for: Connecting pipes of different standards or sizes.

Reducers: Reducer fittings gradually change the diameter from one pipe to the next. These fittings are used to join two pipes of different sizes or pipes and fittings of different sizes. Unlike reducing couplings, reducer fittings can smoothly reduce the flow rate between large and small pipes.

Used for: Connecting pipes of different sizes.

Unions: Union couplings are used to connect two pipes in systems where the pipes are frequently disassembled. The connector consists of a male end, a female end, and a nut that is tightened to create a watertight seal. Unlike a coupling, union connectors can be easily disconnected from the pipe by loosening the nut, making maintenance of the piping system much simpler.

Used for: Connecting two pipes that must be disassembled periodically

Elbow: An elbow fitting redirects flow between two pipes at a given degree. The most common elbows are 45 degrees and 90 degrees, but other configurations are available. Elbows come in two lengths, called short radius and long radius. Short radius elbows are typically used in pressurized applications or where there is not enough room for a long radius elbow. In addition to changing the direction of flow in a system, elbow adapters can be used to join two pipes of different sizes or to join standard pipes.

Used for: Changing the direction of flow

Cross joint: A cross joint has four openings, one inlet and three outlets, or one outlet and three inlets. They are commonly used in hot and cold water systems, drainage systems, and irrigation and sprinkler systems.

Used for: Connecting and diverting flow through two to four pipes

Nipples：Nipple fittings are used to connect two female-threaded pipes or fittings. These fittings contain two male-threaded ends that seamlessly connect to merge two pipes or fittings together. Nipples are available in a variety of configurations. A close nipple contains very little material between the two male-threaded end, meaning a small portion of the fitting is exposed when connecting pipes or fittings. A hex nipple, on the other hand, contains a six-sided section between the two threaded ends so that a wrench can grip them.

Used for: Connecting two female-threaded pipes

Valves: Valves are used to turn on and off the flow of water or regulate the flow of liquid or gas through a system. They come in a variety of configurations, each designed for a specific application. Although a valve is technically a fitting, it is often classified in its own category.

Purpose: To regulate or stop flow in the system.

How to choose the right pipe fitting?

When selecting fittings for your application, you need to pay attention to four details of the pipe: its material, size, pressure rating and connection standards.

Material

The material of the pipe fittings must be compatible with the material of the pipe. In general, the same material should be used for the fittings and the pipes to which they connect. This ensures that both components are suitable for their purpose. Transition fittings are used when pipes of different materials must be joined. These fittings contain one material at one end and another material at the other end. This allows pipes of different materials to be integrated seamlessly as long as the materials are compatible with the intended use.

Size

It is also necessary to determine the correct size. The size of the pipe fitting depends on the inside diameter of the pipe to which it is connected. Common sizes for gas pipes range from 1/4 inch to 48 inches. Measure the outside diameter of the pipe and use a pipe size chart to identify  the right fitting size. Properly sized fittings reduce flow restrictions and minimize pressure drop. Undersized fittings can restrict flow, while oversized fittings waste space and material.

Pressure Rating

Also consider pressure ratings. According to Pipeline Awareness, pipe pressure must be monitored 24 hours a day, 365 days a year. Therefore, fittings must be rated according to the maximum operating pressure of the system. High-pressure applications require stronger, thicker-walled fittings. Using undersized fittings can lead to leaks or even explosive failures. To be safe, make sure the rating is well above your operating pressure.

Fitting Standards

Regulatory agencies set pipe fitting standards to determine how pipes and fittings connect to each other. Some of the most common pipe standards include ANSI, JIS, ISO, DIN, NPT, NPTF, BSPT, BSPP, SAE, UN, and UNF. Because these standards are determined by governing agencies, they vary by location. For example, NPT (National Pipe Thread) is the most popular standard for tapered threaded fittings in the United States. BSP (British Standard Plumbing), on the other hand, is a popular standard in the United Kingdom, Australia, and Commonwealth countries.