Standard Copper Tubing Dimensional Reference

Petersen Does Not Sell Copper Tubing

Select Mechanical or Inflatable Pipe Plugs based on the below tubing ID (Internal Diameter) shown in the copper pipe size chart below, along with the pressure to be blocked.

Copper Tubing Sizes & OD Reference

Copper pipes are widely used in plumbing, HVAC, gas, and water systems, as well as in industrial applications. They are classified by types K, L, M, and DWV, which indicate wall thickness and intended use.

This guide is to help users compare copper pipe sizes across different tubing types with actual measured diameters, including nominal pipe size, outside diameter (OD), inside diameter (ID), and wall thickness. Understanding these differences ensures correct sizing for fittings, Plugs, test equipment, and line maintenance tasks.

Use the copper pipe size chart provided as a reference for plug sizing, pressure testing, and system compatibility. For systems requiring copper pipeline isolation or testing, Petersen Products offers Inflatable Pipe Plugs and hydrostatic test pumps, designed to support copper tubing work safely and efficiently.

Copper Pipe Size Chart

		Type
COPPER PIPE I.D. & WALL THICKNESS CHART
Nominal Pipe Size inches	O.D.	I.D.				Wall Thickness
		K*	L**	M***	DWV****	K	L	M	DWV
1/4	0.375	0.305	0.315	-	-	0.035	0.030	-	-
3/8	0.500	0.402	0.430	0.450	-	0.049	0.035	0.025	-
1/2	0.625	0.527	0.545	0.569	-	0.049	0.040	0.028	-
5/8	0.750	0.652	0.666	-	-	0.049	0.042	-	-
3/4	0.875	0.745	0.785	0.811	-	0.065	0.045	0.032	-
1	1.125	0.995	1.025	1.055	-	0.065	0.050	0.035	-
1-1/4	1.375	1.245	1.265	1.291	1.295	0.065	0.055	0.042	0.040
1-1/2	1.625	1.481	1.505	1.527	1.541	0.072	0.060	0.049	0.042
2	2.125	1.959	1.985	2.009	2.041	0.083	0.070	0.058	0.042
2-1/2	2.625	2.435	2.465	2.495	-	0.095	0.080	0.065	-
3	3.125	2.907	2.945	2.981	3.030	0.109	0.090	0.072	0.045
3.5	3.625	3.385	3.425	3.459	-	.120	.100	.083	-
4	4.125	3.857	3.897	3.935	4.009	.134	.114	.095	.058
5	5.125	4.805	4.875	4.907	4.981	.160	.125	.109	.072
6	6.125	5.741	5.845	5.881	5.959	.192	.140	.122	.083
8	8.125	7.583	7.725	7.785	-	.271	.200	.170	-

*K, thick walled, underground residential, commercial and industrial uses.

**L, medium walled, residential and commercial uses

***M, thin walled, above ground residential and light commercial uses.

****DWV, Drain/Waste/Vent, non-pressurized

The content in this website may be used but with no warranty or liability. These copper tubing sizes and dimensions are believed to be correct but should always be double checked with alternative sources. Strictly adhere to and follow all applicable national and local regulations and practices.

Nominal, Outside, and Internal Diameter Definitions

1. Outside Diameter (OD):

The actual outer dimensions of copper tubing.
For a given nominal size, the OD always remains same for all types of tubing.
A component in critical selection in compression fittings, flare connections, and plug sealing ranges.

2. Internal Diameter (ID):

The flow path dimension inside the tube.
Directly impacted by the wall thickness; the thicker the walls, the smaller the ID, and vice-versa.
Crucial in calculations of fluid volume, pressure loss, and test flow.

3. Nominal vs Actual - The Key Rule:

The 1/2" CTS has an OD of 0.625 inches for Types K, L, and M.
The ID varies depending on the tube variety based on the rating of the wall thickness.

Types of Copper Tubing (K, L, M)

Copper tubing comes in different types - K, L, and M - each designed for specific applications and wall thicknesses.

Type K
Type K tubing has the thickest walls and is ideal for underground water lines, high-pressure applications, and commercial piping where durability is critical.
Type L
Type L tubing offers moderate wall thickness and systems It is generally used for residential space heating, space cooling, and water heating applications.
Type M
Type M tubing has the thinnest walls and is suitable for light duty residential applications, such as indoor water supply and low-pressure piping.

Understanding these types helps ensure proper tube selection for pressure testing, isolation, and maintenance tasks. For copper line work requiring temporary sealing or testing, Petersen Products provides isolation plugs and test tools designed for each tube type.

How Copper Tube Sizing Works?

Wall thickness, defined by the type of tube, K, L, or M, is an important factor when copper lines are exposed to pressure, burial depth, or external loads. Tubes with thicker walls offer greater strength and long-term durability, while thinner walled tubing is suitable for light-duty applications. Understanding the relationship between copper pipe sizes or dimensions, and wall thickness ensures proper plug selection, safe operation, and reliable maintenance of systems.

For operations such as pressure testing, line isolation, or live-line maintenance, Petersen Products provides PeteStop® inflatable line stops, isolation plugs, and hydrostatic test pumps that are compatible with a wide range of copper tubing sizes and types. These solutions ensure secure sealing, reliable performance, and safe handling across plumbing, HVAC, gas, and water systems. Use our copper pipe size chart to select the correct tools and tubing for your application.

Copper Tubing Standards

Copper tubes are manufactured to industry standards that define exact outside and inside diameters, wall thicknesses, and material requirements. Following these standards ensures accurate selection of mechanical or inflatable pipe plugs, reliable pressure testing, and efficient pipeline maintenance.

Key Standards:

ASTM B88: Seamless copper water tubes (Types K, L, M)
ASTM B280: DWV copper tubing for non-pressurized applications.
EN 1057 / ISO 12449: International standards for water and gas systems.

Frequently Asked Questions

What do the letters K, L, M mean on copper tubing?
Ans. The Letters K,L,M Indicated the wall thickness categories of copper tubes, not pressure grades or internal diameter.
Is nominal size the same as measured diameter?
Ans. No. Nominal size is a traditional reference label and does not reflect the physical diameter. OD is the real measured diameter used for charts.
Do gas and water copper lines share the same sizing system?
Ans. Yes. Both gas and water copper lines follow the same Copper Tube Size system, meaning the OD remains consistent for a given nominal size.
Which copper tubing type is commonly used underground?
Ans. Type K is the standard choice due to thicker walls and external load tolerance for the underground installations.
How do I determine the correct copper tubing size for my application?
Ans. Check the nominal size for the pipe system requirements.
> Confirm the OD for fitting compatibility.
> Select wall type (K, L, M) based on pressure, location, and application.
> Consider pipe plugs or isolation tools if the system requires testing or temporary shut-off.