Jointing of copper tubes & pipes, capillary joints

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.

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.

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 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.

When working near to joists and floorboards, glass, paintwork and other pipework with capillary joints it is important to shield these areas with 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 t he 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 following the procedure on page 182 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 t he 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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