PVC pipe is available in Schedule 40 and Schedule 80 varieties. Other than the color and the cost, there is a big difference. You just have to look a little closer to see. We will outline the key differences, and hopefully help you identify which option is the best for your project.
The wall thickness of a PVC pipe or fitting determines its schedule. The thickness also correlates with the amount of pounds per square inch (PSI) that the pipe or fitting can handle.
Schedule 40 PVC is usually white in color and has thinner walls, thus can handle less pressure than it’s counterpart. Schedule 40 PVC pipe works best for low water pressure applications.
By contrast, Schedule 80 PVC is usually gray in color and has thicker walls; therefore, it can handle higher water pressures. Schedule 80 PVC is well suited for industrial and chemical applications.
Although schedule 80 PVC is usually gray, sometimes it can be white. Likewise, while schedule 40 PVC is usually white, sometimes it can be gray. Checking the label of the pipe is the only guaranteed way to determine which schedule PVC you have.
The outside diameter is the same for a schedule 80 and a schedule 40 PVC pipe with the same “nominal” size. The difference lies in the thickness of the walls, thus giving the two schedules different interior diameters and different PSI capabilities.
For example, a 2” schedule 40 PVC pipe has a .154” minimum wall and can handle up to 280 PSI. A 2” schedule 80 PVC pipe has a .218” minimum wall and can handle up to 400 PSI. Both have an outer diameter of 2.375”.
Since the increased thickness of the schedule 80 walls is added internally, it decreases the inner diameter of the pipe. This decrease in the inner diameter results in a slightly more restricted flow for schedule 80 PVC pipe compared to schedule 40 PVC pipe. Due to the thicker walls, schedule 80 PVC is not only able to handle higher PSI, it is also more resistant to bending and breaking than schedule 40 PVC.
Because schedule 40 PVC and schedule 80 PVC pipe have the same outer diameter, you can use schedule 40 PVC fittings with schedule 80 PVC pipe and vice versa. However, it is critical to remember that schedule 40 PVC has a lower maximum PSI rating, and as such, it’s imperative to understand that the entire pipeline system is only as strong as the weakest part. This means using just one schedule 40 PVC fitting lowers the entire PSI of the pipeline, and going above that PSI can lead to the destruction of the pipeline.
If you’re trying to decide which schedule PVC you should use, just consider what your job entails. If you’re using the PVC pipe and fittings for irrigation or for plumbing in your home, schedule 40 PVC will probably get the job done just fine and at a cheaper cost. Although schedule 40 PVC has a lower PSI than schedule 80, it is more than capable of handling the pressures of these more routine types of applications. It’s not necessary to use the higher PSI of the schedule 80 PVC, and schedule 40 PVC is easier on your budget.
If you’re using the PVC pipe and fittings for industrial or chemical applications, you probably need to use schedule 80 PVC. Since these applications can result in higher pressures, thus put more strain on the pipeline, the tougher schedule 80 PVC is a necessity, and the additional cost is a worthwhile investment for all of the above-outlined reasons.
So in summary, the key differences are:
- - Less expensive
- - Fine for more residential plumbing and irrigation uses
- - Has thinner wall thickness (0.154” on a 2” nominal pipe)
- - Can handle up to 280 PSI
- - Usually white in color, but not always
- - A bit more expensive
- - Mainly used for chemical, industrial, and manufacturing purposes
- - Has thicker walls (0.218” on a 2” nominal pipe)
- - Can handle us to 400 PSI
- - Usually gray in color, but not always
You may also come across schedule 80 CPVC, which is even stronger than standard schedule 80 PVC. We’ll address the differences between Schedule 80 PVC and Schedule 80 CPVC in a future blog post.