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Tips to Measure and Install Plumbing Pipes

Having the correct-sized plumbing pipes is essential to installing and replacing parts of your plumbing system. You can easily measure your pipes on your own by a couple of different methods. Once you measure your pipes and you know what kind you will need you can start with the installation process.

Measuring Your Plumbing Pipes

There are two measurements that you should make sure are correct and that you get from your plumbing pipes. This includes the Outside Diameter (OD) and the Nominal Pipe Size (NPS). These measurements are universal to all pipe materials.

Measuring the outside width of your pipe will give you the OD measurement. You will need to cross-reference your OD measurement with an ASME chart in order to find your NPS measurement. NPS measurements are commonly used by plumbers when they talk about and shop for plumbing pipes.

How To Find The Size Of Your Plumbing Pipes

Finding the size of your plumbing pipe can be easy if you already have the pipe in front of you. All pipes will have the NPS either printed or labeled on the pipe itself. Copper pipes will have a label that has what kind of copper material it is made of and plastic piping will have the plastic material name, thickness, and size printed on the side.


How Do You Measure Plumbing Pipes?

There are three methods that you can use to measure your plumbing pipes on your own. The following charts will help you convert your OD measurement to the NPS measurement.

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

If you have access to the open end of your plumbing pipe you can find the direct diameter measurement by putting a ruler or measuring tape directly across the open end of the pipe. If the pipe has already been installed there are other methods that you can use to measure your pipes.

Outside Diameter Measurement

When you have a pipe that has already been installed it is very easy to get the OD measurement. All you need is a pair of calipers. Take the calipers and measure the outside of the pipe to get your OD measurement.

Circumference Measurement

When you use the circumference method to measure your plumbing pipes you will need to do a little bit of math to find the OD measurement.

Wrap a piece of string or flexible tape around your plumbing pipe. Measure the tape or string and write down the measurement. Then divide the circumference measurement by pi (pi=3.1415). This will allow you to find the pipe’s OD. You’ll need to reference the charts to find the pipe’s NPS.

Pipe Installation Tips

It is possible that with some knowledge you can replace or install your own water plumbing pipes. This is best if you have a small area or a single pipe that needs to be replaced. Large plumbing jobs should always be done by a professional.

tip for plumbing pipe insulation

Use PEX Pipes For Installation

PEX piping is great when you have a single pipe that needs to be installed. PEX pipes work really well within your plumbing system and are made of a plastic kind of material. This pipe material is great if you’re looking for an easy installation. They are flexible, cut easily, require only simple fittings, and are less expensive plumbing pipes.


Get The Correct Pipe Size

All components of a plumbing system require very specific pipe sizes. You’ll want to check your local plumbing codes to make sure you get the correct size. Also, measure your pipes so that you can ensure that your plumbing will function correctly.

Ensure Pipe Materials Match

It’s possible for corrosion to begin due to two different metals or materials touching each other. Match the new pipe with the old or current pipe material to avoid these kinds of problems. If you have to get a different pipe material for your installation you will need to use different fittings to attach the pipe.

Check Your Fittings

Pipe fittings are a part of the plumbing system that redirects water flow and attaches two pipes together. Specific fittings work better with different pipe materials. You’ll want to make sure that you are using the kind that works with your pipe material. Checking your fittings will ensure that leaks in your system are prevented.
< h3>Dry-Fit Your Pipes Before You Attach Them

Dry-fitting is the process of checking that a pipe is the correct size prior to permanently attaching it to another pipe. This can help catch any error with the pipe type and size before you attach them for good. Dry-fitting is highly recommended because once you attach your pipes together you may not be able to easily get them apart.

The Adeedo team are experts in installing and repairing plumbing pipe systems. Give us a call today to schedule your pipe installation!

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