Different types of copper pipe to know

Copper piping has a huge and growing range of applications. It is widely used for domestic and commercial gas, water, oil and central heating systems, for underground service supplies and for industrial chemicals.

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Copper pipe connectors and piping have many advantages: they have freed our homes from toxic lead and are increasingly used in green technology. However, not all copper pipe is the same so it is important to choose the appropriate kind.

Sizes and gauges

While the width of a pipe is often chosen in view of pressure considerations and run lengths, the thickness of the metal is mostly a matter of safety. Building regulations, gas safe standards and other codes often specify pipe dimensions suitable for particular applications and responsible trade suppliers like Watkins and Powis will always advise you to ask if you have any doubts about suitability.

Broadly speaking, copper pipe needs a thick wall if it is to be buried underground or if it carries gas in locations where there is a fire risk (which includes our homes). The actual thickness depends on the pipe diameter. ASTM define this category of pipe as “type K” and it can take pressures of about 1900psi. At the other extreme, there are light grades of pipe that offer a cost saving for internal low-risk applications and pressures up to about 980psi (type M in the ASTM scheme). The majority of pipework is intermediate in thickness and can be used for both internal and external runs and pressures up to 1500psi (and sometimes described as type L).

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Each grade is available in a range of diameters, but the most common by far is 15mm copper pipe followed by 22mm and 28mm. The larger sizes are often used for baths and storage tanks. Note that these are external measurements so if you are doing calculations to determine pressures and flow rates you need to subtract the thickness.

Soft v Hard

Copper is harder than lead but soft enough to easily bend, flex and route round obstructions. Its softness also makes it easy to flare onsite or to get a good seal from compression fittings. Flame free installation methods are a great safety benefit when working with gas. Copper can also be hardened and hard copper pipe is preferable for long runs or any location where the pipe may be exposed to impact. Hardened copper is also preferred for refrigeration.