PVC, or polyvinyl chloride, is a common material for pipes and electrical conduit. It’s a durable, cost-effective plastic that’s used in a wide variety of applications.
But not all PVC is created equal. You’ll often see PVC pipes and conduit listed as either “Schedule 40” or “Schedule 80,” which can be confusing. What’s the difference, and which one should you use?
This article will break down the differences between Schedule 40 vs 80 PVC, focusing on key factors like wall thickness, pressure rating, common applications, and cost. By the end, you’ll have a clear understanding of which schedule is right for your project.
What do Schedule 40 and Schedule 80 mean?
When you’re dealing with pipes, you’ll often hear about “pipe schedule.” Pipe schedule is a standardized way of describing how thick the wall of the pipe is relative to its diameter.
A Schedule 80 pipe will always have a thicker wall than a Schedule 40 pipe of the same nominal pipe size (NPS).
How is pipe scheduling used?
The schedule number tells you something about how much pressure the pipe can handle. Because Schedule 80 pipe has a thicker wall, it can withstand greater pressure than Schedule 40 pipe.
For any given NPS, the Outer Diameter (OD) of Schedule 40 and Schedule 80 pipe is the same. However, because Schedule 80 pipe has that thicker wall, its Inner Diameter (ID) will be smaller than the ID of Schedule 40 pipe.
Material Properties and Performance: A Detailed Comparison
The key difference between Schedule 40 and Schedule 80 pipe comes down to a single factor: wall thickness. That difference in thickness translates to a range of performance characteristics.
Wall Thickness and Pressure Rating
The schedule number of a pipe indicates its wall thickness. A Schedule 80 pipe has a thicker wall than a Schedule 40 pipe of the same nominal size. This added thickness means that Schedule 80 pipe can withstand higher internal pressures.
In general, Schedule 80 pipes are more resistant to pressure than Schedule 40 pipes. The thicker walls of Schedule 80 pipe also provide increased resistance to strain and chemicals.
Applications Based on Strength and Resistance
Because of its lower cost and adequate strength, Schedule 40 pipe is suitable for applications where pressure requirements are relatively low. Common uses include drainage and low-pressure irrigation.
Schedule 80 pipe, on the other hand, is better suited to applications that involve higher pressures, elevated levels of strain, or exposure to corrosive chemicals. It’s also more durable and able to withstand physical damage, which makes it a good choice for demanding applications in industrial settings.
Schedule 40 vs. Schedule 80 Pipes and Fittings for Plumbing Applications
So, when do you use Schedule 40 and when do you use Schedule 80 for plumbing?
Common Plumbing Uses for Each Schedule
Schedule 40 pipe is great for residential water supply lines, drainage, and irrigation systems. It’s an economical choice when you don’t need to worry about extremely high pressure or harsh conditions.
Schedule 80 pipe is a workhorse that’s often used in industrial settings and chemical processing plants. It can handle higher pressures and temperatures than Schedule 40, so it’s the one to choose when things get intense.
Installation Considerations
The good news is that you can install Schedule 40 and Schedule 80 pipe in much the same way. Just be sure to use fittings that are compatible with the schedule you’ve chosen. You wouldn’t want to use Schedule 40 fittings with Schedule 80 pipe, or vice versa.
Color Coding and Identification
Here’s a quick tip: Schedule 40 pipes are usually white, while Schedule 80 pipes are often gray. But don’t rely on color alone! Always double-check the markings on the pipe to be sure you’re using the right schedule for the job.
Schedule 40 vs. Schedule 80 Conduit for Electrical Applications
Both Schedule 40 and Schedule 80 PVC conduit can protect electrical wiring, but they’re not interchangeable. Understanding their strengths can help you choose the right one for your project.
When to Use Each Schedule for Electrical Conduit
If you’re wiring a residence or a light commercial space, Schedule 40 PVC conduit is usually strong enough. It’s a good choice when the cables aren’t likely to be exposed to significant physical damage.
Schedule 80 PVC conduit is more durable, so it’s better for applications where the conduit might be struck or damaged, such as in an industrial setting.
Cable Compatibility
Several types of cable work well in either type of conduit. NM cable, THHN/THWN wire, and XHHW wire are commonly used, depending on the specific application.
It’s important to know that the National Electric Code (NEC) has specific rules for different applications, so always consult the NEC before you begin your project.
Cost and availability
Schedule 80 pipes and conduit usually cost more than Schedule 40 because they’re made with more material. For example, Schedule 80 conduit can be 20% to 50% more expensive, depending on the manufacturer.
Even though Schedule 80 is more expensive upfront, consider the long-term cost. The durability and resistance of Schedule 80 might prevent costly repairs or replacements down the road. You’ll have to weigh the costs versus the benefits for your specific project.
Frequently Asked Questions
What is the difference between Schedule 40 and Schedule 80 PVC pipe?
The main difference lies in their wall thickness. Schedule 80 pipe has a thicker wall than Schedule 40. This results in Schedule 80 being stronger and able to handle higher pressure applications. Both have the same outside diameter, so fittings are interchangeable. However, because Schedule 80 has a thicker wall, its inside diameter is smaller than Schedule 40.
When should Schedule 80 pipe be used?
Schedule 80 pipe should be used in applications where higher pressure ratings are required. It’s commonly used in chemical processing, industrial applications, and systems where the fluid temperature is higher. If you’re dealing with compressed air lines, or any system where the pressure exceeds the limits of Schedule 40, then Schedule 80 is the safer, more reliable choice. It’s also a good idea to use Schedule 80 where the pipe is more likely to experience physical impact or abrasion.
Summary
Schedule 40 and Schedule 80 pipes differ in wall thickness, pressure rating, cost, and suitability for different applications. When choosing between them, be sure to carefully think about the pressure requirements, the likelihood of physical damage, and your budget.
Always consult relevant codes and standards to ensure your pipe installation is safe and compliant.