Joining copper pipe is one of the basic plumbing skills. Compression and capillary joints are easy to make and once you’ve mastered the techniques, you’ll be prepared for a whole range of plumbing projects.

Connecting pipes effectively is the basis of all good plumbing as most leaks result from poorly constructed joints. For virtually all domestic plumbing purposes you will only have to use compression or capillary joints. Compression joints are easy to use but expensive, while capillary joints are cheap but need some care in fitting.

If you are making a join into an existing pipe system remember to make sure the water supply has been turned off at the relevant stop-valve and the pipe completely drained.

Preparing the pipes
Before joining pipes together, check that the ends are circular and have not been distorted. If they have been dented, cut back to an undamaged section of the pipe using a hacksaw with a sharp blade or a wheel tube cutter.

Use a file to make any correction and remove ragged burrs of metal. If you’re using a capillary joint clean up the sides of the pipe with abrasive paper or steel wool

What size of pipework and fittings?
Pipework is now sold in metric dimensions, but plumbing in your home may be in imperial sizes. The metric sizes are not exactly the same as their imperial equivalents which shows the different ways pipe can be bought.

These differences can cause problems. With capillary joints you have to use adaptors when converting pipe from one system to another. Adaptors are also needed for some compression joints although the 12mm, 15mm, 28mm and 54mm sizes are compatible with their imperial equivalents. This means if you already have imperial compression joints you can connect in new metric pipework, without replacing the joints.

Adaptors are made with different combinations of metric and imperial outlets to fit most requirements. A supplier will advise on what replacements to use.

Flux and solder
Essential in the soldering operation, flux is a chemical paste or liquid which cleans the metal surfaces and then protects them from the oxides produced when the blowtorch heats the copper so a good metal-solder bond is formed. Mild non-corrosive flux is easy to use as it can be smeared onto the pipe and fitting with a clean brush or a sliver of wood. Although it is best to remove any residue this will not corrode the metal. There is an acid-corrosive flux which dissolves oxides quickly, but this is mostly used with stainless steel. The corrosive residue must be scrubbed off with soapy water.

Solder is an alloy (mixture) of tin and lead and is bought as a reel of wire. Its advantage in making capillary joints is that it melts at relatively low temperatures and quickly hardens when the heat source (blow-torch) is removed.

Blow-torches
A blow-torch is an essential piece of equipment when making capillary joints. It is easy, clean and safe to use providing you handle it with care. Most modern torches operate off a gas canister which can be unscrewed and inexpensively replaced (larger cans are relatively cheaper than small). Sometimes a range of nozzles can be fitted to give different types of flame, but the standard nozzle is perfectly acceptable for capillary joint work.

Using a blow-torch
When using a blow-torch it’s most convenient to work at a bench, but you’ll find most jointing work has to be carried out where the pipes are to run. Pipework is usually concealed so this may mean working in an awkward place, such as a roof space, or stretching under floorboards. However, always make sure you are in a comfortable position and there’s no danger of you dropping a lighted blow-torch.

When working near to joists and floorboards, glass, paintwork and other pipework with capillary joints it is important to shield these areas with flame-proof glass fibre matting.

Applying the heat
When making a capillary joint gradually build up the temperature of the copper by playing the flame up and down and round the pipe and then to the fitting. When the metal is hot enough the solder will melt and you can then take away the flame. The joint is complete when a bright ring of solder appears all round the mouth of the fitting. Stand the torch on a firm level surface and turn it off as soon as you have finished. Where two or more capillary joints are to be made with one fitting, for example the three ends of a tee, they should all be made at the same time. If this is not possible wrap a damp rag round any joints already made.

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