Malleable Iron Pipe Fittings Guide - RS Components

Modern life relies on water and gas supply as well as sewage and wastewater removal, and underground piping supports these mechanisms. In industry, gases and liquids are moving around plants and factories through pipework, too. Holding all of this piping together is durable pipe fittings. 

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In this guide, we explain what malleable iron pipe fittings are, their uses and the types and sizes of fittings that can be found.

One of the basic methods for creating any object from metal is known as casting, and that’s how malleable iron pipe fittings are made. Casting is when the metal is heated until it is molten and it is then poured into a mould in the desired shape. After it is left to cool or is cooled forcibly, it returns to its solid form but in the desired shape. It can then be finessed with various finishes, and have screw threads tapped into it.

In the case of malleable iron pipe fittings, when being formed, the temperatures used to form these fittings can reach as high as 250 degrees Celsius and under a pressure of between 150–300psi. This balance of pressure and heat allows electrons to leave and enter the metal, this then creates a layering effect in the metal composition or structure and is what causes the metal to be flexible and mouldable.

Because of malleable iron pipe fittings’ bendable structure, the metal itself is not as strong as other fitting options. Due to this factor, malleable fittings are not used when further welding is required, as the reheating of the metal would affect its composition and threading is often formed on the fittings instead of additional welding. However, the heating process of malleable iron fittings means that they have great tensile strength, making them a very durable tool and allowing them to last years, if not decades.

Malleable Iron Pipe Fitting Dimensions

The choice of fitting doesn’t just end with composition, as there is a range of dimensions to choose from when selecting the correct malleable iron pipe fitting.

Firstly, the pipe sizes run from 1/8th of an inch, or 6 mm, all the way up to 6 inches, or 150 mm. Between those, there are many different dimensions to choose from. For the smallest size at 6 mm, the common dimensions range from 6.4 mm to 25.4 mm, or 0.25 inches to 1 inch. To give an idea of increasing scale, in the largest fitting size at 6 inches or 150 mm, the dimensions can range from 1.2 inches to 8 inches, or 32.5 mm to 204.8 mm.

As well as size, iron pipe fittings also differ in shape. They come in angles of 45 degrees to 90 degrees. 

In terms of types of fittings, these include:

• Tee fittings, which are T-shaped
• Elbow fittings – where the metal is bent and resembles the elbow of an arm – straight couplings and caps
• Concentric coupling which is straight, but one end of the fitting is larger than the other

When it comes to connecting pipework, malleable iron pipe fittings are not the only fittings that are available, and there is a wide variety of options depending on need and task. For example, in heavy industrial use, wrought iron or forged iron fittings could be a more appropriate choice. Forged fittings are more robust than malleable fittings and are made of thicker metal. They also come in much larger sizes than malleable fittings, as they are more commonly used in applications where the metal needs to be stronger and more durable against large pressures of liquid or gas being transported. Unlike iron fittings, forged fittings can come in a range of metals, including nickel, steel and others.

Another alternative to malleable fittings is carbon steel fittings. These fittings are heavier than malleable fittings and are used in a wide range of applications where durability is paramount. However, unlike malleable iron pipe fittings, carbon steel piping and fittings cannot be used to transport liquid, as it releases particles that would affect the quality of the liquid being transported. Also, due to its more robust nature, carbon steel fittings are a better choice when welding is involved in connecting piping. Much like malleable fittings, carbon steel fittings come in a range of sizes, dimensions and types, depending on the task needing to be completed.

Types of Piping Systems

Most homes built since the mid-s have plastic pipes and fittings, which are rated by the American Society for Testing and Materials (ASTM). Plastic pipes can be used for pressurized applications, such as potable (drinking) water systems, hot- and cold-water distribution, and irrigation systems. They can also be used for nonpressurized applications (gravity flow), such as sewage, drainage and storm drain systems. Homes built prior to used galvanized steel or cast-iron pipes for drain/waste/vent (DWV) systems. DWV systems remove wastewater and prevent the flow of sewer gases into homes. The most common types of plumbing pipes used in homes today are copper and polyvinyl chloride (PVC), both of which are strong, long lasting and easy to install. Other choices include chlorinated polyvinyl chloride (CPVC) and PEX pipe.

Copper Pipes vs. CPVC Pipes

Whether copper or CPVC piping should be used to deliver a home’s drinking water will vary from home to home. Here are some pointers to help you determine the best choice:

• Water Types: In many areas, particularly those without municipal water sources, the acidity of the home’s water may be a factor in choosing the right types of plumbing pipes. Highly acidic water can break down copper pipes over time and cause green staining in fixtures. Although passive water filters can deal with acidity, they must be recharged every year or so. Because of this, owners sometimes opt for acid-indifferent CPVC piping.
• Installation Time: CPVC must not be pressured for 24 hours after installation to allow the pipe adhesive to set properly. Copper can be used within minutes of installation.

PEX Pipes

PEX pipes differ from traditional rigid pipes in one obvious way: They’re flexible. This makes it easier to snake them to different areas of a home. Using PEX piping may require running more pipe, but it also involves fewer fittings. PEX crimp tools offer a simple way to make these flexible fittings more secure and watertight.

Here are a few other advantages of PEX:

• It’s quieter than rigid piping.
• It has a smooth interior that resists scale buildup and corrosion, which can affect pipe flow over time.
• It’s freeze-break resistant, although not freeze-proof. PEX tools, such as specialty expansion kits, will enhance this benefit by absorbing dimensional changes caused by thermal expansions/contractions.
• PEX systems have appealing installation costs compared to rigid materials.
• PEX piping is often used in green buildings, installed either as a remote manifold or plumbing system.

PEX pipe and crimp fittings, with all their benefits, do have a drawback: Because UV exposure causes a reaction with polyethylene, it isn’t suitable for outdoor use. The maximum level of UV exposure is typically no more than 60 days, but this varies by manufacturer. Using PEX for underground water supplies isn’t ideal, even if UV exposure is decreased.

Have PEX specialty tools on hand to ensure you can make full use of PEX piping advantages.

Materials for DWV Pipes

• Cast-iron pipe and fittings (black)
• PVC Schedule 40 (SCH 40) DWV pipe and fittings (white; used in irrigation, underground sprinkler systems, swimming pools, outdoor applications and cold-water supply lines)
• Acrylonitrile butadiene styrene (ABS) DWV pipe and fittings (black, common in the western US)

Materials for Pressurized Systems

• PVC Schedule 40 (SCH 40) pipe and fittings (white; straight, angular turns; designed for potable water under pressure into buildings)
• Copper tube size (CTS) chlorinated polyvinyl chloride (CPVC) pipe and fittings (cream or tan, used for hot or cold water, sized similarly to copper pipe sizes)
• PVC Schedule 80 (SCH 80) pipe and fittings (dark gray, withstand higher pressure, designed for the distribution of pressurized liquids)

PVC SCH 40 DWV Pipe and PVC DWV Fittings for Nonpressurized Applications

PVC DWV fittings can be installed with foam core pipe or dual-marked solid wall pipe. ASTM F 891-rated foam core pipe is lighter and less expensive. Solid wall PVC pipe is often rated for both pressurized (ASTM D ) and nonpressurized (ASTM D ) applications (often referred to as dual marked). When solid wall or foam core pipe is used with PVC DWV fittings, the resulting system isn’t pressure rated.

Description

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• White, rigid pipe and fittings
• Joined with solvent cement, conforming to applicable ASTM standards
• Have a gradual, sanitary turn

Application

• Draining household sanitary waste (kitchen, bathroom) and groundwater
• Not for pressurized applications or compressed air/gases
  

Joining Method

• Solvent cements must meet ASTM D standard
• Primer is required
• May be joined with a slip-joint compression fitting (a trap adapter)
• Threading PVC 40 pipe isn’t recommended
• Male iron pipe (MIP) and female iron pipe (FIP) size adapters are available

PVC SCH 40 Pipe and Fittings for Pressurized Applications

Description

• White, rigid pipe and fittings
• Joined with solvent cement, conforming to ASTM D standard
• Straight, angular turns
• Not for gradual sanitary turns for pressure systems

Application

• Distributing potable water under pressure into a building (not to be used inside)
• Irrigation and sprinkler systems
• Draining condensate waste from heating and air conditioning systems
• Not for compressed air or gases

Joining Method

• Solvent cements must meet ASTM D standard
• Primer required
• May be flanged with SCH 80 flanges
• Threading PVC 40 pipe isn’t recommended
• MIP and FIP adapters are available

PVC SCH 80 Pipe and Fittings for Pressurized Applications

Description

• Dark gray, rigid pipe and fittings
• Joined with solvent cement conforming to ASTM D standard
• Straight, angular turns must be used

Application

• Distributing pressurized liquids
• Can be used in industrial applications
• Not for use with compressed air or gases

Joining Method

• Solvent cements must meet ASTM D
• Primer should be iron pipe size (IPS) P-70 or Oatey Industrial Grade
• May be flanged with SCH 80 flanges
• Threading PVC 80 pipe can be done
• MIP and FIP adapters are available

ABS Foam Core SCH 40 DWV Pipe and ABS DWV Fittings for Nonpressurized Applications

Description

• Black, rigid pipe and fittings
• Joined with solvent cement conforming to ASTM D standard
• Fittings have a gradual sanitary turn

Application

• Draining household sanitary waste (kitchen, bathroom) and groundwater
• Not for use with pressurized applications or compressed air/gases

Joining Method

• Solvent cements must meet ASTM D standard
• Primer isn’t recommended
• May be joined with a slip-joint compression fitting (a trap adapter)
• Threading ABS-40 foam core pipe isn’t recommended
• MIP and FIP adapters are available

CTS CPVC Pipe and Fittings for Pressurized Hot- and Cold-Water Applications

Description

• Cream or tan, rigid pipe (with a gold stripe) and fittings
• Joined with solvent cement conforming to ASTM F 493 standard

Applications

• Distributing hot and cold potable water under pressure
• Not for use with compressed air or gases
  

Joining Method

• Solvent cements must meet ASTM F 493 standard
• Yellow FlowGuard Gold cements may be used without primer, where approved by code
• Compression fittings with a brass ferrule may be used
• Threading the pipe isn’t recommended; use CTS CPVC male adapters in cold-water applications only; use CTS CPVC brass-threaded transition fittings for hot-water applications

Don’t use compression fittings with brass ferrules to connect to CTS CPVC pipe or fittings where water temperatures exceed 140 degrees Fahrenheit.

Choosing Correct Pipe Sizes

Plumbing beginners often purchase pipes that are too small. To avoid this mistake, it’s helpful to understand the difference between actual measurements and nominal measurements. The word “nominal” roughly means “in name only.” For example, if you need a pipe that has an actual diameter of 1/2 inch, the one you purchase may not be labeled as a 1/2-inch pipe.

Next, identify what kind of plumbing pipe you’re using. Copper, plastic/steel and cast-iron pipes all require different sizing conversions. Knowing your piping material will help you convert your pipe’s nominal measurement to its actual measurement.

Nominal copper pipe sizes are 1/8 inch less than the outer-diameter measurement. Cast-iron pipes’ nominal sizes are around 1/3 inch less than their outer-diameter measurement. Plastic and steel pipes’ nominal sizes use the same conversion and are around 1/3 inch less than their outer-diameter measurement.

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