What are Standard PVC Pipe Sizes?
PVC (polyvinyl chloride) pipes are the most preferred pipes in modern plumbing for their many advantages over other types of pipes. Apart from plumbing, they are also used in construction and industrial applications.
One challenge that most folks face when buying PVC pipes is identifying their sizing. There are different sizes of PVC pipes and measuring them is not as easy as you would think.
When buying PVC pipes, you have to consider the following:
- Nominal pipe size (NPS)
- Outside diameter (OD)
- Internal diameter (ID)
- Wall thickness
- Schedule (schedule 40 or 80)
- Pressure rating
Is PVC Pipe Sizes By ID or OD?
PVC pipe sizes are identified using their inside diameter (ID) but not to the exact decimal point. The inside diameter is rounded off to the nearest whole number. For example, the actual inside diameter of a 3-inch PVC pipe is 3.042 inches, and 3.998 for a 4-inch pipe.
PVC pipes are manufactured, categorized and sold using what is called Nominal Pipe Size (NPS). However, few people know what nominal pipe size is, or even how to measure it.
The term Nominal Pipe Size (NPS) identifies the inside diameter of a pipe with a non-dimensional number. For example, a 2-inch (nominal) schedule 40 PVC pipe has a inside diameter of 2.047 inches and outside diameter of 2.375 inches.
Interestingly, a 2-inch (nominal) schedule 80 PVC pipe has an inside diameter of 1.913 inches but the outside diameter is similar to that of the same size schedule 40 pipe.
How does the nominal pipe size change with increase in the size of the pipe? Let us look at the dimensions of a 5-inch pipe.
A 5-inch schedule 40 PVC pipe has an inside diameter of 5.016 inches and an outside diameter of 5.563 inches. A schedule 80 pipe of the same size has an inside diameter of 4.813 and an outside diameter equal to that of a schedule 40 pipe.
Surprisingly, from 14 inches onwards, the nominal pipe size is equal to the outside diameter of the pipe. For example, 14-inch PVC pipe (nominal) has an internal diameter of 12.41 inches and an outside diameter of 14 inches.
You can see how confusing it is, and that is why it is better to use a chart. Since measuring the outside diameter of a pipe is easy, you can use it to determine the pipe’s nominal pipe size or even internal diameter.
To know the size of the PVC pipe you have, measure its inside diameter. Its nominal size will be the closest whole number. For example, if you get, 6.031 inches, you have a 6-inch pipe. Alternatively, measure the outside diameter then use a PVC pipe chart to get the nominal size.
Schedule 40 PVC Pipe Dimensions Chart
|Nominal Pipe Size (Inches)||Inside Diameter||Outside Diameter||Wall Thickness||Pressure Rating (PSI)|
Schedule 80 PVC Pipe Dimensions Chart
|Nominal Pipe Size||Inside Diameter||Outside Diameter||Wall Thickness||Pressure Rating (PSI)|
PVC Nominal Pipe Size
As I have already mentioned, nominal pipe size (NPS) is a North American standard for indentifying pipe sizes in non-specific terms using the inside diameter with a non-dimensional number.
As I am sure you will agree, it easier saying “This is a 2-inch PVC pipe” than “This a 2.375-inch PVC pipe”. That is why the nominal pipe size standard is used.
This system also brings about standardization in the construction, plumbing and other industries.
Without it, people would be identifying pipes using outside diameter or inside diameter and as I am sure you know, people tend to get different figures during measurement.
The good thing is if you are overwhelmed by this nominal pipe size standard, you can simply measure the outside diameter of your pipe then use the charts above to easily tell what size your pipe is.
Alternatively, you can measure the outside diameter only but when you go to the hardware store clearly let the attendant know that it is the outside diameter of your pipe. Due to their many years of experience, they will know the exact size of your pipe.
As a matter of fact, most professionals don’t even need to measure a PVC pipes (or any other pipe) to tell their size. They can tell the size of a pipe by just looking at it.
Nominal pipe size of a pipe is derived by getting the inside diameter of the pipe then rounding it off to the nearest whole number. For schedule 40 PVC pipes, the inside diameter is usually slightly larger than the nominal size but in schedule 80 PVC pipes the inside diameter is slightly smaller than the nominal size.
Although I said that you derive the nominal size by rounding off the internal diameter to the nearest whole number, that only applies to big-diameter PVC pipes. For small diameter PVC pipes, you round off the internal diameter to the nearest proper fraction.
For example, a ½-inch schedule 40 PVC pipe has an inside diameter of 0.602 inches. The nearest proper fraction is ½ and hence its nominal size.
PVC Pipe Schedule
Another term that confuses folks when talking about PVC pipe sizes is the schedule. In simple terms, schedule in PVC pipes refers to the thickness of the pipe.
There are 2 main types of schedules for PVC pipes. That is schedule 40 and schedule 80 PVC pipes. More on that in this post.
The difference between schedule 40 and schedule 80 PVC pipes is that schedule 80 PVC pipes have thicker walls than schedule 40 pipes. For ease of identification, schedule 40 pipes are usually white while schedule 80 PVC pipes are gray.
The extra thick walls in schedule 80 PVC pipes mean they can handle more pressure than schedule 40 pipes. For example, a 2-inch schedule 40 PVC pipe has a pressure rating of 280 psi, while a similar size of a schedule 80 pipe has a pressure rating of 400 psi.
Although both schedule 40 and schedule 80 PVC pipes have the same outside diameter, the extra thickness in schedule 80 pipes means that they have a smaller inside diameter.
A 2-inch schedule 40 PVC pipe for example has an internal diameter of 2.047 while the same size of a schedule 80 pipe has a diameter of 1.913 inches.
The wall thickness of PVC pipes increases as the size of the pipe increases. For example, the wall thickness of a 2-inch schedule 40 pipe is 0.154 inches while that of a 6-inch pipe is 0.280 inches.
Because, both schedule 40 and 80 PVC pipes have the same outside diameter, you can connect them together. But should you?
Remember that both of these pipes have different pressure ratings and therefore different applications. Schedule 40 PVC pipes are primarily used in plumbing while schedule 80 PVC pipes are used in high-pressure applications like in manufacturing and chemical industries.
You can therefore add a schedule 80 pipe or fitting to a system of schedule 40 PVC pipes and fittings, but you shouldn’t connect a schedule 40 pipe to a network of schedule 80 PVC pipes and fittings.
As always, a connection is as strong as its weakest link. A schedule 40 fitting would be a weak link in a connection of schedule 80 PVC pipes and fittings.
Related: Types of PVC pipes.
And basically those are the dimension charts for PVC pipes. I hope that this guide was helpful to you.
Note: A specific type of PVC called chlorinated PVC or CPCV pipes are available in both nominal pipe size and copper tube size. Carefully check the dimensions used if those are the pipes you want to buy.