How to choose the right copper pipe and fittings

Copper pipe is the traditional choice of pipework for domestic water lines and drain and vent lines. It is available in four types – K, L, M and DWV. DWV is less common nowadays and is usually only found in older properties where it has not been upgraded.

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How copper pipe types vary

Type K is the thickest copper pipe available, at 28mm, followed by Type L at 22mm and finally, Type M is the thinnest at 15mm. Types K and L are available as rigid or flexible piping, whilst M is only available in rigid form.

Most internal domestic plumbing applications require 15mm or 22mm copper piping, with 28mm pipe usually being reserved for mains water supplies. It is always recommended that you replace piping on a like-for-like size basis.

Choosing copper pipe fittings

There are four different copper pipe fittings available, although the one that you choose will vary, based on the type of copper pipe that you are using for your application and whether it is flexible or rigid.

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All types of copper pipe can be soldered, which is the process by which metal surfaces are joined together through the use of heated and cooled solder.

Types K, L and M can also be connected using press-connect and push-fit fittings. Both methods are flameless and involve the use of special connectors to join the pipes. Press-connect fittings are more complex and are therefore usually only installed by professionals. However, most competent DIYers will be happy to use push-fit fittings, which are available from specialists such as

Flexible Type K and L copper pipes can also be connected by means of a flare joint. This is a T-shaped connector that joins three pipes to form a secure joint .


A professional plumber will provide all of the pipework and fittings that are necessary to complete the job in the most efficient manner. A competent DIYer should satisfy themselves that their chosen pipe is of the correct size, and use an appropriate fitting to secure it.

Niru Eilish


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