Measuring your plumbing pipes can be a tough task if you’re unfamiliar with exactly how to do it. This can cause the installation of pipes to be difficult. Here we will share everything you need to know about measuring your plumbing pipes and give you tips on installing them.

How Are Plumbing Pipes Measured?

Because there are many different kinds of pipes, they are measured differently. There are two measurements that plumbers are the most concerned about when measuring pipes. This includes the Nominal Pipe Size (NPS) and the Outside Diameter (OD).

The OD is the width of the outside of the pipe. In order to find the NPS you will cross reference the OD with an ASME chart. Keep in mind that your OD is not the NPS. The NPS is how plumbers will describe and shop for fittings and pipes.

How Can You Tell What Size Pipe You Have?

The easiest way to tell what size plumbing pipes you have is to look at the pipe itself. All plumbing pipes and fittings will have the NPS printed or labeled on the pipe. For instance, copper pipes will have what kind of copper pipe it is and the NPS labeled on it. All plastic pipes will have the size, wall thickness, and kind of plastic it is printed on the side.

How To Measure For Pipe Sizes

There are a few different ways to measure the size of your pipes and we’ll go over each of them. You’ll need the following charts to convert your OD measurement into the NPS.

 

Copper Pipe NPS Reference Chart

Copper Pipe Size	Outside Diameter	Pipe Circumference
1/2″	5/8″	2″
3/4″	7/8″	2-5/8″
1″	1-1/8″	3-1/4″
1-1/4″	1-3/8″	4-1/8″
1-1/2″	1-5/8″	5-1/8″
2″	2-1/8″	6-5/8″
3″	3-1/8″	9-3/4″
4″	4-1/8″	13″

 

PVC, ABS, CPVC, Brass, and Steel Pipe NPS Reference Chart

Plastic/Metal Pipe Size	Outside Diameter	Pipe Circumference
1/2″	7/8″	2-5/8″
3/4″	1-1/8″	3-1/4″
1″	1-3/8″	4-1/8″
1-1/4″	1-5/8″	5-1/4″
1-1/2″	1-7/8″	6″
2″	2-3/8″	7-1/2″
3″	3-3/8″	11″
4″	4-3/8″	14-1/8″

 

Direct Diameter Measurement

In order to measure your pipe’s direct diameter, you will use a measuring tape or ruler and measure across the end of the pipe. However, since you need access to the open end of your pipe, if the pipe is installed already, you may not be able to measure it this way.

Outside Diameter Measurement

Take a set of calipers and measure the outside diameter of the pipe. This is a great option if you’re not able to get to the open end of your pipe.

Circumference Measurement

The third way that you can measure your pipes is to measure the pipe’s circumference. You can do this by wrapping a flexible tape or string around the pipe. You then need to convert the pipe’s circumference into the diameter measurement.

 

Measure the length of your string or tape that went around the pipe and divide that measurement by pi (pi=3.1415). This will give you the OD and you can use the charts to cross-reference to find the NPS.

Tips For Installation

Taking on your own pipe installation can be a good thing if you’re just looking to repair a single broken or old pipe. However, larger jobs should be left up to a professional. Here are some tips for installing water lines.

Begin With PEX Pipes

PEX is a plastic pipe material. It is much cheaper than other materials such as copper. It’s also easy to cut, flexible and has the ability to be connected together with simple fittings. PEX is a great option if you’re replacing a smaller section of your water pipes. This kind of material will make your project run much smoother as the installation is much easier.

Make Sure You Have The Correct Pipe Size

Since you’ve learned exactly how to measure your pipes, getting the correct size should be a breeze. It’s important to use the correct pipe size for your specific project as the size of each matters greatly. Ensure that you’re using the right size and make sure to check your local codes as well for info.

Try To Avoid Mixing Materials

When some materials come into contact with each other they can corrode much faster. This is due to a reaction between the two metals or materials. It’s especially important to pay attention to what the old pipes are made out of to avoid this. If you’re not able to help mixing the two kinds of materials, then a special fitting will need to be used to prevent problems.

Take In Account The Fittings

A fitting is used where two pipes are joined together, usually to change the direction of the water. If the fittings are not adhered together correctly it will likely result in a leak. This is one of the more challenging parts of installing water pipes. Different pipes will require different kinds of fittings. For example, PEX pipes can have clamps or push-on fittings while copper pipe fittings will need to be soldered together.

Dry Fit Before Connecting

Once you cut your pipe it is essential to make sure that your pipe is the correct size before making the final connection. This is why you need to dry fit the pipe first regardless of what type of material your pipes are.

The experienced professionals at Proskill can help you make your pipe installation process smoother. Give us a call today to schedule your installation!