WHEN TO USE SCHEDULE 80, SCHEDULE 40 OR CPVC-LINED

03, Mar. 2026

 

WHEN TO USE SCHEDULE 80, SCHEDULE 40 OR CPVC-LINED

When highly corrosive chemicals are used in industrial processing applications, chlorinated polyvinyl chloride (CPVC) is often specified. Depending on the unique system conditions and applications, different CPVC piping variations—such as schedule 80 piping, schedule 40 piping, or even CPVC-lined FRP—may be recommended. While uncommon, Schedule 40 and Schedule 80 piping may be used together under certain conditions. The piping must be the appropriate schedule for the application. Some plumbing systems, for example, would require greater pressure resistance in one part but not another. The piping materials must also be compatible.

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Always consult with a certified engineer and piping manufacturer when specifying pipe and use this guide to learn about the general differences between the three options to help determine the CPVC type that is ideal for your application.

Piping Schedule

Nominal Pipe Size (NPS) is a North American set of standards for piping used in high pressure and temperature applications. NPS identifies pipe using two criteria:

  • Outside Diameter: A dimensional number referring to the width of a pipe opening from the outer edge to the other outer edge 180° across.
  • Pipe Schedule: A non-dimensional number reflecting the thickness of the pipe wall.

The thickness of a CPVC pipe wall is defined by the ASTM F441 Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Pipe, Schedules 40 and 80, and is dependent on the outside diameter of a pipe.

In other words, the “schedule” distinction is nominal only, and not an actual dimensional measurement. The wall thickness increases as a pipe’s outside diameter increases. Two tables below show the specific wall thickness values of schedule 40 and schedule 80 piping based on the pipe’s outside diameter.

Corzan® CPVC pipe and fittings are available in schedule 40 and schedule 80 nominal pipe sizes (NPS).

Pressure Bearing Capabilities

The schedule distinction was put in place in part to help engineers and architects understand a pipe’s pressure bearing capabilities. Schedule 80 piping’s increased wall thickness enables a higher pressure rating than schedule 40 piping.

Learn about how CPVC pipe pressure ratings are calculated in our resource article, "How CPVC Pipe Pressure Ratings Are Calculated."

Applications

Corzan Industrial Systems often recommends Schedule 80 piping be specified for pressurized systems that are exposed to high temperatures. The additional wall thickness also increases the impact resistance of the pipe, and enables the piping to maintain pressure bearing capabilities longer in systems where highly aggressive, corrosive substances are used.

The thinner wall of schedule 40 CPVC, when compared to schedule 80, results in a lower pressure rating at all temperatures. Thus, when the pressure rating requirements of a system are low, but corrosion resistance is critical, schedule 40 CPVC piping may be specified. This includes certain venting or plumbing applications.

For fume handling systems and other non-pressure situations, CPVC ducting is the geometry of choice. The wall thickness of CPVC ducting is even less than that of schedule 40 piping, but the chemical resistance is maintained.

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While uncommon, Schedule 40 and Schedule 80 piping may be used together under certain conditions. The piping must be the appropriate schedule for the application. Some plumbing systems, for example, would require greater pressure resistance in one part but not another. The piping materials must also be compatible.

Pipe Measurements and Pressure Rating Tables

When comparing measurements of schedule 80 and schedule 40 CPVC piping, only the outer diameter of the pipe remains consistent.

For example, both 1 in. pipes have an outer diameter of 1.315 in. But, the minimum wall thickness, average inner diameter, pipe weight and maximum water pressure vary.

The following tables can guide engineers on the proper pipe size and schedule based on pressure and other factors.

When to Use CPVC-Lined Fiberglass Reinforced Plastic (FRP)

Another variation of CPVC piping often used for industrial applications is CPVC-lined fiberglass reinforced plastics (FRP). FRP piping does not use the NPS set of standards, as these pipes are custom built for more specialized conditions that have a specific set of requirements.

CPVC-Lined FRP Advantages

In an application where CPVC material offers necessary corrosion resistance, but standard schedule 80 piping does not meet the system’s pressure or temperature requirements, CPVC-lined FRP piping may be specified. A CPVC-lined fiber-reinforced polymer (FRP) piping system, sometimes called a "dual laminate," is an FRP pipe lined inside with CPVC for necessary corrosion resistance. The CPVC adds a corrosion-resistant layer against processing chemicals, while the FRP provides the pipes with structural integrity.

The CPVC liner offers a corrosion resistant layer against the processing chemicals, while the FRP provides the structural integrity needed to meet the pressure rating and temperature requirements of the system.

View the Corzan Chemical Resistance Table for CPVC's compatibility with 400+ chemicals. 

The Cost of CPVC-Lined FRP

The performance of CPVC-lined FRP in high pressure and high temperature environments is why it’s specified over Corzan Schedule 80 and Schedule 40 CPVC piping. The reason FRP is not universally recommended in CPVC-compatible applications is its respective cost.

CPVC-lined FRP piping systems are custom made for each installation, not manufactured in bulk. While this helps to instill reliability that the system is compatible with the process, installation and fabrication is more labor-intensive—both in number of installers and time required. Each piece must be wrapped, and sometimes even hand-laid in the field.

Though the additional expense can be a drawback, FRP piping can provide significant, long-term cost-savings advantages. For example, CPVC-lined FRP has replaced titanium systems in corrosive, high pressure, high temperature environments. When compared to these exotic metals, CPVC-lined FRP translated to material savings without hindering performance or reliability.

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Types of FRP Fitting and Their Applications - OCEANFRP

Fiberglass-reinforced plastic (FRP) fittings are essential in various industries due to their superior corrosion and chemical resistance. These fittings are crucial links within FRP piping systems, ensuring materials’ structural integrity and efficient flow. Utilized across the United States and globally, FRP fittings are favored for their strength-to-weight ratio and durability, contributing to an extended service life.

FRP fittings are engineered to withstand harsh environments where traditional steel pipes may corrode, making them ideal for process piping in chemical plants, power plants, and wastewater treatment facilities. Their design often incorporates a corrosion barrier, structural layer, and resin system, including vinyl ester or epoxy, enhancing their mechanical properties and operating temperature range. In this post, we’ll discuss the types of FRP fittings and their applications.

FRP Fittings Overview

FRP fittings are a group of pipe fittings manufactured from fiberglass-reinforced plastic, a composite material known for its lightweight and alkali-resistant properties. These fittings are designed to connect sections of FRP pipes, forming a leak-proof and resilient network capable of handling various media. The diverse range of FRP fittings includes standard shapes and custom configurations to suit the unique demands of each application.

The design of FRP gratings, such as the filament wound laminate or the chopped strand mat, contributes to their tensile strength and ability to accommodate thermal expansion. Material and resin selection is tailored to the application’s needs, ensuring each fitting performs optimally under the expected conditions, including exposure to aggressive chemicals or extreme temperatures.

FRP fittings offer superior corrosion resistance compared to steel piping, significantly enhancing their design life. This is particularly beneficial in environments where steel or carbon steel may degrade quickly. Furthermore, including components such as woven roving and glass fiber enhances the structural shapes, ensuring they maintain their integrity even under axial loads.

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Types of FRP Fittings

FRP fittings encompass various shapes and sizes, including wye connections, elbows, tees, couplings, reducers, crosses, flanges, adapters, unions, and bends. Each is designed to fulfill a specific function within FRP piping systems, from changing the flow direction to connecting pipes of different diameters. With their corrosion-resistant nature and glass-fiber reinforced construction, these fittings are pivotal in maintaining continuous and efficient operations in various industrial settings.

Wye Connections

Wye connections are specialized pipe fittings that create a branch line at a 45-degree angle from the main FRP pipe. This design reduces friction and turbulence in the flow of fluids or gases, thereby maintaining system efficiency. Wye connections are used extensively in residential and industrial plumbing, sewer, and waste management systems.

Elbow 

Elbows are curved pipe fittings that enable FRP pipes to turn corners or change direction. They come in various angles, the most common being 45-degree and 90-degree turns. Elbows are crucial in systems where space is limited and a straight run of pipe is impossible, ensuring that pipelines can be routed around obstacles while minimizing pressure loss.

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Tees

Tees are T-shaped pipe fittings that join three sections of FRP pipes. Their main function is to split a flow into two directions or combine two flows into one. They are indispensable in applications where multiple fluid streams are manipulated, such as in water distribution networks or chemical processing systems.

Coupling

Couplings are pipe fittings that connect two pieces of FRP pipe. These simple but essential fittings extend the length of a pipe run or repair a broken or leaking section. They come in various types, including flexible couplings that accommodate minor misalignments and rigid couplings for a firm connection.

Reducer

Reducers are pipe fittings that connect two FRP pipes of different diameters, allowing a smooth transition between sizes. They are vital in systems requiring a change in the flow rate or pressure of the conveyed material. Reducers help maintain an optimal flow velocity, preventing erosion or cavitation.

Crosses

Crosses are four-way pipe fittings that create a junction point where FRP pipes from four different directions converge or diverge. They are less common than tees but are used in specialized applications where multiple fluid streams need to intersect, such as intricate process piping networks.

Flange

Flanges are circular pipe fittings that connect FRP pipes to other components, such as valves or pumps, or join two sections of pipe together. They are designed with a flat surface that can be bolted together, creating a secure and accessible joint that can be easily disassembled for maintenance or inspection.

Adapter

Adapters are pipe fittings that facilitate the connection of FRP pipes to dissimilar materials or different piping systems. They are critical in transitions where a change in diameter, thread type, or pipe material occurs, ensuring compatibility and a leak-proof seal between the different sections.

Union

Unions are pipe fittings that allow for the quick disconnection and reconnection of FRP pipes without cutting. Like flanges, unions consist of three components: a nut, a female, and a male end. They are particularly useful in piping systems requiring frequent cleaning or maintenance disassembly.

Bend

Bends are fittings that facilitate directional change in FRP piping systems. They are similar to elbows but have a smoother, more gradual curvature, which allows for less turbulent flow and reduced pressure drop. Bends are commonly used in applications where space allows for a wider turn radius, optimizing flow dynamics.

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Features of FRP Fittings

FRP fittings are renowned for their robust mechanical properties, including high tensile strength, corrosion and chemical damage resistance. These characteristics make them suitable for various demanding applications, ensuring the safe and efficient transport of fluids and gasses.

Durable and High-Strength

FRP fittings are engineered for longevity and high performance. The combination of glass-fiber reinforced thermosetting resin and strategic material and resin selection results in durable and strong products. This durability is critical to maintaining the integrity of FRP flat panels over time, even in the face of corrosive chemicals and variable temperatures.

Corrosion Resistant

FRP fittings, crafted using the filament winding process, are renowned for their exceptional corrosion resistance. Unlike carbon steel, FRP pipes do not succumb to the deteriorative effects of harsh chemicals. This inherent corrosion resistance significantly extends the service life of FRP equipment, making it a cost-effective choice for many industries.

Lightweight and Easy to Install

The lightweight nature of FRP fittings greatly simplifies handling and installation processes. Workers can easily maneuver and fit these components without heavy lifting equipment, reducing installation costs. Their lightness, combined with their robustness, makes them an attractive alternative to traditional materials.

Easy Installation and Customization

Fiberglass pipe fittings are easy to install and can be customized to meet the demands of various applications. For example, the ability to create a long-term chlorine header solution showcases the versatility and adaptability of FRP pultruded profile in complex installations and corrosive environments.

Applications of FRP Fittings

Due to their durability and corrosion resistance, FRP fittings have various applications across diverse industries. They serve critical infrastructure, processing, and utilities functions, demonstrating adaptability and reliability in various environments.

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FRP Pedestrian Bridges

FRP fittings are an excellent choice for pedestrian bridges. They offer abrasion resistance and the ability to withstand environmental elements. Their durability ensures a long-lasting structure, which is especially beneficial for high-traffic areas.

Wastewater and Water Treatment

FRP fittings are indispensable in wastewater and water treatment facilities. They resist the corrosive effects of treatment chemicals and provide a durable solution for piping systems essential to these operations.

Military

The military relies on FRP fittings for their robustness and corrosion resistance. These characteristics are crucial in demanding environments where equipment reliability and longevity are of the utmost importance.

Cooling Towers

FRP fittings find extensive use in cooling towers, where their resistance to moisture and chemicals ensures efficient operation and a reduced need for maintenance.

Oil and Gas

The oil and gas industry benefits from using FRP fittings. These fittings withstand the corrosive substances encountered in extraction and processing, ensuring safe and continuous operations.

Plant and Chemical Processing

Chemical processing plants utilize FRP fittings to maintain the integrity of their systems in the presence of aggressive chemicals, thereby safeguarding against leaks and potential hazards.

Utilities

Utility providers incorporate FRP fittings into their systems because they are long-lasting and resistant to environmental stress, ensuring reliable service to the community.

Mining

Mining operations favor FRP fittings because they are strong and resistant to the corrosive and abrasive materials often found in the process.

Agricultural

Agricultural industries use FRP fittings for irrigation and water management systems, benefiting from their resistance to various elements and longevity.

Architectural

Architecturally, FRP fittings contribute to a design’s aesthetic and functional aspects, offering creative solutions that are both durable and resistant to weathering. FRP grating platforms and handrails have a variety of applications in the architectural sector.

Golf Courses

FRP fittings are utilized in golf course maintenance, particularly in water features and irrigation systems, providing a low-maintenance, rust-free solution to landscaping needs.

Theme and Water Parks

FRP fittings are sought after in theme parks and water parks for their ability to withstand harsh chemical exposures and constant water contact. They are used in applications such as water slide constructions, splash pads, and piping systems for water rides. Their lightweight nature simplifies the installation process in the intricate designs of theme park attractions, ensuring a safe and durable infrastructure for visitors to enjoy.

Pulp and Paper

The pulp and paper industry benefits from FRP fittings due to their resistance to corrosion and ability to handle various chemicals used in the paper production process. These fittings are used in pipelines that transport caustic and acidic fluids, where traditional materials would deteriorate quickly. The durability of FRP ensures a longer lifespan for the systems and a reduction in maintenance costs, making them an economical choice for the industry.

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Wrap-Up!

In conclusion, the variety of available FRP fittings provides engineers and designers with the tools to create efficient and resilient systems for many applications. From custom corrosion solutions in harsh chemical environments to utilizing standard FRP pipe configurations for water treatment facilities, the adaptability of FRP fittings ensures they meet the demands of various industries. Their inherent characteristics, such as durability and resistance to corrosion, make them a reliable choice for long-term installations.

The versatility of FRP fittings is evident in their widespread use across diverse sectors. Whether it’s reinforcing the infrastructure of a golf course or ensuring the safe transport of substances in a chemical processing plant, FRP fittings play an essential role. Acknowledging the significance of FRP fittings in modern construction and maintenance projects is pivotal for any industry looking to enhance efficiency and reduce maintenance costs over time.

For more FRP Pipe Fittingsinformation, please contact us. We will provide professional answers.