How And What To Measure For PVC Pipe Projects

How And What To Measure For PVC Pipe Projects

If you are carrying out a project with PVC pipe either for plumbing purposes or to build something you will need to know how to accurately measure your pipe and fittings. 

We look at how you can take the correct measurements of the PVC pipe length for accuracy and the success of your project. This applies to both plumbing and non-plumbing work. 

Use An Appropriate Tape Measure

Before you begin your PVC pipe project it’s important to make sure that all your measurements are correct. 

To do this you will need to have the right tape measure. This is one that you can place inside the pipe joints and connectors for accurate measurements of the PVC pipe dimensions. 

If your tape measure is too big it will be more difficult to take measurements from inside the PVC fittings and connectors. 

While a larger tape measure will suit bigger connectors and joints if you are using joints that are less than an inch in diameter you will need a smaller tape measure. 

This is important because the accuracy of your project depends on the dimensions of the pipe and joints being correct. 

To make sure you have the right size for measuring both the inside diameter and outside diameter, use a small and large tape measure. 

Pipe Sizes

Depending on the type of project you are doing you will need to choose one of the best PVC pipe sizes.

PVC pipe comes in a range of diameters from ½ inch up to 24 inches wide, known as the nominal pipe size (NPS). 

You may be using this for a plumbing project, building a piece of furniture, or creating a scale model. Whatever the use, there will be an appropriate PVC pipe size for your needs. 

The other consideration will be how thick the walls of the PVC pipe will be.

Again, depending on what you are constructing you will need to choose something that is quite flexible or something that is more resilient and strong. 

There are therefore three measurements that you will need to take into account when checking measurements for your PVC projects - the internal diameter, the outer diameter and the wall thickness of the pipe. 

Internal Diameter

The internal diameter of a PVC pipe is the greatest distance between the two inside walls.

Be aware, this measurement will vary according to the schedule of the pipe. It will also be important when you come to join the pieces of pipe together with joints and connectors.

The diameter of the interior of the pipe will also affect how much it bends. Pipes with a small internal diameter will be easier to bend if you need this for your project. 

Smaller pipes will not be as robust or able to hold any real weight so only use them for plumbing or non load bearing projects. 

Pipe Schedules

Most PVC pipes come in three schedules, 40, 80 and 120. A pipe schedule is a term that relates to the thickness of the pipe walls.

As the schedule gets larger the walls of the pipe get thicker and the internal diameter of the pipe gets smaller. 

Schedule 40 is good for most domestic pressurized and non-pressurized jobs, and good for non-plumbing projects.

Schedule 80 is better for pressurized work and recognized by its gray rather than white color.

Schedule 120 is the thickest type of pipe and can be used for non-corrosive or less reactive corrosive substances. 

Outer Diameter

PVC pipe measurements are calculated on a nominal scale. This means that the measurement relates to the category of pipe rather than to a specific numerical measurement. 

To calculate the outer diameter of PVC pipe measure from the outside edge of the cross-section of pipe to the other outside edge. 

You will then need to refer to a scale for the average outer diameter to get the correct size of the pipe. 

For instance, if your measurement of the outer diameter is 4 inches this translates to a 3 ½ inch pipe size, if your measurement was 3 ½ inch diameter then the pipe size would be 3 inches. 

Wall Thickness

The wall thickness of PVC pipe is mostly determined by the schedule of the pipe. 

A schedule 40 pipe will have a thickness of 0.154 inch on a 2-inch nominal pipe. This is more than adequate for most domestic plumbing applications able to withstand up to 280 psi.

A schedule 80 PVC pipe will have a thicker wall as it is more suitable for commercial and industrial use. A 2-inch nominal pipe of this type will have a wall thickness of 0.218 inch. 

It can withstand higher pressure, up to 400 psi and can transport chemicals and industrial waste water. 

Joints And Connectors

When it comes to fitting your PVC pipe project together you will need to use joints and connectors.

Measuring these elements correctly is central to the whole project and if the measurements are out then your project will not work as it should. 

Joint depths will be very important to measure especially when you are working up to a fixed structure.

You will see a lip on the inside of the fittings and this is where the pipe will stop when joined to that particular fitting. 

So that you cut your pipe to the correct length, you need to take this joint depth into account when calculating the length by adding it on for each joint or connector. 

Elasticity

If your project requires your PVC pipe to bend or curve you will need to use smaller diameter pipe such as ½ inch or 1 inch. Any larger than these and you will find it difficult to get the pipe to bend. 

To ensure that the bend in your pipe is retained you will need to make sure it is strongly fixed at either end.

This is because the PVC pipe that has been bent will try to return to its original shape i.e. straight, even after fixing. If the fitting is not secure it will come loose. 

PVC pipe can be bent by heating it or by applying pressure. Be careful as it can snap back and cause injury if not secured. Use cement or screws for a solid hold on bent PVC pipe. 

Cutting

Before cutting your PVC pipe double-check your measurements and remember to include the portion of the pipe that will slide into the joints and connectors in your calculations. 

To cut PVC pipe you can use a hacksaw or a specialist pipe cutter. 

A hacksaw has small, fine teeth and will give you more control over the cut.

A pipe cutter looks like a pair of pruning shears with a large cutting blade and usually operates via a ratcheting or scissor system. 

Some burring may occur on your PVC pipe after cutting. This can be removed with a sharp knife and sanded down further if needed.

This will also help when you apply PVC cement to adhere the pipes together.

In Conclusion

Preparation is the most important part of any project and taking accurate measurements is central to understanding what size PVC pipe you have. 

For your PVC fitting to work, take the time to make careful measurements of pipes and fittings for a successful project. 

We hope this guide on how and what to measure for your PVC project has been helpful. 


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