What the difference between Iron Pipe Size / Nominal Pipe Size vs. Copper Tube Size?

Iron Pipe Size (IPS) was the first pipe size sytem used plumbing systems. With the introduction of Copper Piping, Copper Tube Sizes (CTS) came on the scene, followed by CPVC and PEX.

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It is important to know what piping sizing system you are working with when ordering fittings and valves. Fittings, designed for IPS will not work on CTS piping or tubing and vice versa.

Iron Pipe Size (IPS) - Carbon Steel, Red Brass, 304 / 316 Stainless Steel & PVC. IPS is prevalent in general piping and industrial applications.

Copper Tube Sizes (CTS) - Copper, CPVC & PEX. CTS is specific to plumbing and potable water systems.