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.

A compression joint, as its name implies, is made by compressing two brass or copper rings (known as olives or thimbles) round the ends of the pipes to be joined, so forming a watertight seal. There are two main types of compression joint – the non-manipulative fitting and the manipulative fitting.

Although not the cheapest means of joining a pipe, a non-manipulative joint is the easiest to use and requires only the minimum of tools. It comprises a central body made of brass or gunmetal with a cap-nut at each end which, when rotated, squeezes the olive tightly between the pipe end and the casing. This is the most commonly used type of compression joint suitable for most internal domestic plumbing purposes,

A manipulative joint is now rarely used in indoor domestic water systems. Because it applied to the olive so that it does not buckle under the strain of tightening.

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 – check the table right) 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.

Capillary joints

A capillary joint is simply a copper sleeve with socket outlets into which the pipe ends are soldered. It is neater and smaller than a compression joint and forms a robust connection that will not readily pull apart.

Because it is considerably cheaper than a compression joint it is frequently used when a number of joints have to be made and is particularly useful in awkward positions where it is impossible to use wrenches.

Some people are put off using capillary fittings because of the need to use a blow-torch. But modern gas-canister torches have put paid to the fears associated with paraffin lamps and are not dangerous.

How a capillary joint works

If two pipes to be joined together were just soldered end to end the join would be very weak because the contact area between solder and copper would be small. A capillary fitting makes a secure join because the sleeve increases this contact area and also acts as a brace to strengthen the connection. Molten solder is sucked into the space between the pipe and fitting by capillary action, and combines with a thin layer of copper at the contact surface thus bonding the pipe to the fitting. To help the solder to ‘take’ the copper needs to be clean and shining. Therefore flux is applied to prevent oxides forming which would impair the solder-copper bond.

Types of capillary joint

The most common type of capillary joint has a ring of solder pre-loaded into the sleeve. It is known as an integral ring or ‘Yorkshire’ fitting – the name of a leading brand.

The ‘end feed’ type of capillary joint is virtually the same as an integral ring fitting. But you have to add the solder in a separate operation. The sleeve is slightly larger than the pipe and liquid solder is drawn into the space between by capillary action.


Capillary fittings are.

– cheap to buy.

– unobtrusive when fitted.

– useful in confined spaces.

– very quick to install – and to unmake during alterations, BUT

– using them requires a blow-torch to melt the solder

– if the joint leaks you have to completely remake it.

Compression fittings are.

– easy to assemble – you’ll only need two wrenches or adjustable spanners – BUT

– they’re much more expensive than capillary fittings

– they are much bulkier and obtrusive on exposed pipe runs

– in awkward places you may not be able to get wrenches in to tighten up the joint. Leaks can sometimes be cured by further tightening.


Matching new pipe to old isn’t always as easy as it sounds because even if your existing pipework is copper it may have been manufactured to imperial sizes – and all new copper pipe comes in metric sizes.

– if you’re using integral-ring capillary fittings (where the solder is pre-loaded into the fitting) you’ll always need special adaptors to join new copper pipe to old -these adaptors are just ordinary fittings with one end slightly larger than the other.

– end-feed capillary fittings can be made to work simply by adding more solder – but it requires more skill.

– if you’re making compression joints, the 12mm, 15mm and 28mm fittings will work with old 3/8in, 1/2in and 1 in pipe. For other imperial pipe sizes, again you’ll need special adaptors.


When using a blow-torch always.

– wear thick heat-resistant gloves.

– put down a lighted blow-torch on a firm flat surface with the flame pointing into space

– clear any flammable material from the area where you are working 6 f

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 even a finger. 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.


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 flames, 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.


For cutting pipe:.

• hire a wheel tube cutter (which ensures perfectly square pipe ends) or use a hack saw.

– use a metal file for removing ragged burrs of metal and for squaring ends of pipe that have been cut with a hacksaw. A half-round ‘second-cut’ type is ideal.

For compression joints:.

– use two adjustable spanners or pipe wrenches (one to hold the fitting, the other to tighten the cap-nut).

– steel wool to clean the surface of pipes before assembling a joint.

For capillary joints:.

– a blow-torch to melt the solder.

– steel-wool for cleaning pipe surfaces.

– flux to ensure a good bond between the solder and copper

– solder because even if you’re using integral ring fittings (which already have solder in them) you may need a bit extra

– glass fibre or asbestos mat (or a ceramic tile) to deflect the torch flame from nearby surfaces.


For a perfect fit, pipe ends must be cut square. If you’re using a hacksaw, hold a strip of paper round the pipe so its edges align and saw parallel to the paper edge. Use the same trick if you have to file an inaccurately-cut end.


With capillary fittings, the heat you apply could melt the solder in nearby fittings. To help prevent this, wrap them in wet cloths.

When working near to joists and floor-boards. Glass, paintwork and other pipework with capillary joints it is important to shield these areas with glass fibre matting or a piece of asbestos.

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.

Repairing a compression joint

If a compression joint is leaking and tightening of the cap-nut doesn’t produce a watertight seal you’ll have to disconnect the fitting and look inside – after turning off the water supply. If a cap-nut is impossible to move, run a few drops of penetrating oil onto the thread. If that doesn’t do the trick, you’ll have to cut it out and replace the fitting and some piping.

Once you have unscrewed one of the cap-nuts there will be enough flexibility in the pipe run to pull the pipe from the casing. Usually the olive will be compressed against the pipe. First check that it is the right way round and if it isn’t replace it with a new one making sure that it is correctly set.

Sometimes the olive is impossible to remove and needs to be cut off with a hacksaw – make the cut diagonally. Reassemble the joint and repeat the operation for the other end of the pipe. Turn on the water supply to check that the repair is watertight.

Repairing a capillary joint

Poor initial soldering is usually the reason why a capillary fitting leaks. You can try and rectify this by ‘sweating’ in some more solder but if this doesn’t work you’ll have to remake the joint.

Play the flame of the blow-torch over the fitting and pipe until the solder begins to run from the joint. At this stage you can pull the pipe ends out of the sockets with gloved hands. You can now reuse the fitting as an end feed joint or -replace it with a new integral ring capillary connection.

If you reuse the fitting clean the interior surface and the pipe ends with abrasive paper or steel wool and smear them with flux. Then follow the procedure for making an end feed capillary joint.

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