Polyvinyl chloride (PVC) is a versatile material with multiple uses that includes pipes. PVC pipes are not one-size-fits-all. Before starting a project, it’s a good idea to double-check the piping size. It will save you money on time and materials in the long run.
The three classifications of PVC pipes are schedule 40, schedule 80, and schedule 120. The pipes use a nominal measuring system. The measurements are based on structure type instead of a specific size. This means if you need a 0.96” PVC, you’ll need to cut a one-inch pipe to size.
Along with size, the PVC category also indicates the pipe’s specific use. If you’re new to PVC piping or just want to brush up on your knowledge, keep reading for a complete understanding.
How to Measure the Outer Diameter
The nominal system means the outer diameter (OD) is larger than what is listed on the pipe. It can be a little confusing, but it’s designed to make it easier to choose the right size. For example, all one-inch PVC pipes will fit 1” openings.
A tip to remember is all schedule 40 and schedule 80 PVC pipes have the same outside diameter. It differs for schedule 120 PVC.
When you measure the outside diameter of a PVC pipe, you want to follow a few steps. It ensures you get an accurate measurement.
- Find the widest opening at the end of the pipe.
- Measure from one edge of the opening to the other.
The resulting measurement is the outside diameter. Now you know if the PVC pipe is the right size for the fitting.
Make sure you measure all PVC piping before starting a project. Measurements can differ according to the manufacturer.
The Difference Between Schedule and Class PVC Pipes
PVC pipes are divided into two ratings, schedule, and class. It helps to understand the terms, so you choose the right pipe for the job.
This is the older rating system used when the iron pipe size system (IPS) was the standard. The system has 3 classifications,
- Standard (STD) – Schedule 40
- Extra strong (XS) – Schedule 80
- Double extra strong (XXS) – Schedule 120
The rating refers to the strength of the PVC pipe walls. The higher the number, the stronger the PVC. There is a disadvantage to the rating system. Wider openings mean thinner pipe walls. It’s something to consider when you’re shopping for PVC piping.
Instead of focusing on wall strength, class concentrates on the pipe’s ability to withstand pressure. It is a newer rating system some people feel is an improvement over schedule classifications.
The pipe’s class is the amount of pressure it can withstand indefinitely. It’s usually listed in a 2:1 ratio to also indicate the maximum amount of pressure it can endure for a short period, usually during an emergency.
An example is a PVC pipe with a 200 class rating. It means the pipe is designed for 200 psi but can handle up to 400 psi for a little while.
It’s recommended that you try to use the class system. It gives you a better idea of what the PVC pipe can handle. The schedule system is also fine, as long as you understand how the material is classified.
Schedule 40 PVC Piping
Most schedule 40 PVC piping is grey or white, but you can find the material in other colors. The pipes are thinner than schedule 80 and schedule 120 and used for specific purposes.
Schedule 40 PVC pipes are thinner to allow liquids to flow freely. It can withstand cold water and temperatures around 140 degrees Fahrenheit.
The most common use for the pipes is for water and gas lines around homes and offices, and drainage. With a 120 – 180 psi pressure rating, the pipes are often found in pools, golf courses, and spas.
Another use for schedule 40 PVC pipes is making percussion instruments. It’s also when you see the different colors being used. The pipes are capable of producing a range of musical tones.
Schedule 80 PVC Piping
Normally dark grey, schedule 80 PVC pipes are thicker than schedule 40 ones. The pipes can handle pressure between 210 – 1230 psi. Their uses include wastewater treatment, deionized water lines, chemical processing, and industrial plating.
Schedule 80 pipes are thicker than schedule 40. The pipes are ideal to use as support on construction sites or when a longer pipe is needed.
The pipes may not be the best choice for general water or liquid flow. The thicker walls can slow down the flow.
Schedule 120 PVC Piping
Schedule 120 PVC piping is noticeably thicker than schedule 40 and schedule 80. The density of the pipe’s walls makes it ideal for use in corrosive and non-corrosive applications. Construction and automotive facilities often use the pipes due to their durability.
The pipes have a psi rating between 380 – 1,010.
Schedule 120 pipes are most often used in commercial and industrial settings. The pipe’s thickness is ill-suited for most home use. Properties with deep wells, around 100ft, can use the piping to bring water up. A 1.5Hp motor is also needed to bring the liquid up through the pipe.
Compared to schedule 40 PVC piping priced around $0.40, schedule 120 pipes are priced noticeably higher. It is also harder to find the piping at your local hardware store.
Don’t Forget About Schedule 30 PVC Pipes
Schedule 40, schedule 80, and schedule 120 are the most commonly used sizes of PVC pipes, but they’re not the only ones. You also have the option of using schedule 30 pipes.
The walls are thinner on schedule 30 pipes, not strong enough for most pressure. These pipes are generally used in gravity-fed systems like gutters.
Along with schedule 40, schedule 30 PVC piping is inexpensive and ideal for crafts and building outdoor furniture.