The ability to join lengths of pipe to each other and to other plumbing fittings is a basic skill that must be acquired by every amateur plumber. Light gauge copper and
stainless steel tubing is commonly used in hot and cold water supply. The easiest way to join pipes of these materials is with non-manipulative (type A) compression joints and fittings.
The basic compression coupling — for joining two lengths of pipe of the same diameter — consists of a joint body with, at each end, a brass or copper ring or olive and a screw-on cap-nut. When a tube end is thrust into the joint and the cap-nut tightened, the olive is compressed against the tube wall to make a watertight connection. As well as straightforward couplings there is a very wide range of other compression joints and fittings to meet virtually every plumbing need.
There are T junctions (usually referred to simply as tees) for use in taking a branch water supply pipe from an existing pipeline. There is a variety of bends, crosses and couplings with a compression joint at one end and a threaded joint (either male or female) at the other for connecting to screwed fittings, to cold water storage cisterns or to hot water cylinders. There are straight and bent tap and ball-valve connectors. These have a compression joint at one end and a ‘cap and lining’ joint at the other. Then there are plumbing fittings such as stop-cocks and gate valves that are manufactured with compression joint inlets and outlets.
All of these joints and fittings — and many others — can be seen at any good DIY centre and in the pages of the manufacturers’ illustrated catalogues.
The only essential tools required to make compression joints are a hacksaw, a metal file and a couple of reliable wrenches but, where a project will necessitate making a number of joints, a wheel tube cutter can be a great time saver. You should also have a tin of jointing compound such as ‘Boss White’ and some vaseline or oil. A piece of chalk will be useful too in helping you make your first joints effectively.
How to make a simple coupling
First cut the tube ends squarely either with a hacksaw or a wheel tube cutter. A useful tip to ensure a square cut with a hacksaw is to join the edges of a piece of newspaper together around the pipe at the point where the cut is to be made and to use the paper as a template.
Remove all burrs. Wheel cutters usually produce internal burr which can be removed with the reamer incorporated in the tool. A hacksaw produces external burr that must be removed with a file.
Dismantle the compression coupling and slip first the cap-nut and then the olive over the tube end. Make sure that you don’t turn the olive round as you slip it on the pipe end. With some makes it doesn’t matter but with others it is most important that the olive should be the right way round in the completed joint.
Push the tube end into the body of the fitting until the tube stop permits it to go no further. Smear some jointing compound on the olive and apply a little oil or vaseline to the screw threads of the joint body. It must be said that some manufacturers of compression fittings insist that no jointing compound is necessary when making their joints. However, it can do no harm and does ensure a watertight joint at first attempt.
Push the olive up to the joint body and screw on the cap-nut hand tight. Mark the tube end with a piece of chalk and make another mark on the cap-nut immediately adjacent to it. Hold the body of the coupling firmly with one wrench and — using the
Modem homes usually have single-stack drainage systems. All wastes discharge into a single main soil and waste stack. This is usually made of plastic and is constructed within the fabric of the building, only a few inches of open vent pipe protruding from the roof Even where this system is installed it is quite usual — as the illustration shows — for ground floor sinks, baths or basins to discharge over a yard gully.
Once you have gained a little experience you’ll find that you can take one or two short cuts when making compression joints. It won’t be necessary to dismantle the couplings completely or to make the joint at each end of the coupling separately. Loosen the two cap-nuts. Thrust the two pipe ends through the olives into the body of the coupling. Then, after tightening up the cap-nuts hand tight, use one wrench on one and one on the other to tighten them both up at the same time. You’ll find too that, after you have successfully made two or three joints, you’ll be able to tighten by those one and a quarter turns without needing the chalk guide.
Inserting a tee junction into a vertical length of pipe — to take a branch to an outside tap or a washing machine for instance — can be difficult at times. Follow these instructions and you’ll find that it is quite easy.
Cut off the water supply and drain the pipe. Cut a 19mm (3/4in) segment out of the pipe at the point at which the tee is to be inserted. Even though you have drained the pipe properly it is likely that a pint or so of water will flow out as you cut the pipe. Don’t be alarmed but do be prepared to catch it!
Dismantle the cap-nuts and olives from the straight run of the tee. Slip a cap-nut and then an olive up the upper length of cut pipe. They’ll promptly slide off again unless you secure them. Use a spring clothes peg for this. Slip the other cap-nut and olive over the end of the lower length of cut pipe. Use another spring clothes peg to prevent them slipping down.
Spring the two cut ends of pipe into the body of the tee and screw up the cap-nuts as already described to make the joint. Make sure, before you finally tighten up, that the branch outlet of the tee is pointing in the right direction — towards the position of the garden tap or washing machine.
Stainless steel tubing
Stainless steel tubing is obtained in the same sizes as copper tubing and is joined by type A compression joints in exactly the same way. When cutting stainless steel tubing it is better to use a hacksaw than a tube cutter and, since stainless steel is harder than copper, you’ll find that a little more force is needed to tighten up the cap-nuts effectively.
Most manufacturers make a range of chromium plated brass fittings for use with stainless steel tube and one manufacturer makes fittings of stainless steel for this.
Pipe sizes and metrication
Prior to metrication, the sizes of copper and stainless steel tube encountered in British domestic plumbing were 1/2in, 3/4in and lin. These were measurements of the internal diameter of the pipes. The 1/2in pipe was commonly used for the rising main and for branch hot or cold water supplies to sinks, basins and bidets, and for the branch supply to the lavatory flushing cistern. The main hot and cold supply pipes to the 3/4in bath taps would be in 3/4in pipe. This size was also used for the vent pipe from the hot water storage cylinder and — usually — for the cold supply pipe from the cold water cistern to the cylinder. A lin diameter pipe was used for the flow and return pipes
between boiler and cylinder. Occasionally, too, the cold supply pipe from storage cistern to cylinder would be in the larger lin diameter pipe.
The metric equivalents of 1/2in, 3/4in and 1in tube are 15mm, 22mm and 28mm respectively and all compression joints are now sold in these metric sizes. They are not — as a glance at any rule with both metric and imperial measurements will confirm — exact translations of the imperial sizes. However, most of the difference is accounted for by the fact that the imperial dimensions were of the internal diameter while the metric measurements are of the external diameter of the pipes.
Fortunately for the amateur plumber the 15mm and 28mm metric sizes are sufficiently close to their imperial equivalents to permit compression fittings of these sizes to be used, without adaptation, with 1/2in and lin copper or stainless steel tubing. When using a 22mm fitting to join modern 22mm tubing to existing 3/4in tubing, some kind of an adaptor is necessary. The exact way in which the fitting is adapted will depend upon its make. Generally, it will involve using a larger olive and perhaps a larger cap-nut with the same joint body. Ask the supplier if you are in doubt.
In some parts of the country a corrosive water supply produces a phenomenon called dezincification in the brass of which compression fittings are usually made. Brass is an alloy of copper and zinc and, when dezincification takes place, the zinc dissolves away leaving a fitting unchanged in appearance but totally without strength.
The remedy used to be to use gunmetal fittings since gunmetal — an alloy of copper and tin — is not affected by dezincification. There is, however, nowadays a range of corrosion resistant brass fittings which are unaffected by dezincification. They are clearly marked CR on body and cap-nuts.
When purchasing compression fittings it is wise to ask the supplier for the kind of fittings that are used by good quality plumbers in your particular area.
Soldered capillary joints and fittings provide an alternative to compression fittings for joining copper or stainless steel tubing. Soldered capillary fittings are smaller, neater and cheaper than compression types.
A capillary coupling — the basic capillary joint — is a metal sleeve that fits closely over the ends of the lengths of tube to be joined. The coupling is then heated, and molten solder encouraged to flow — by capillary attraction — into the narrow space between the outside of the tube end and the inside of the coupling.
There are two kinds of soldered capillary fittings on the market. Integral ring fittings incorporate within their body sufficient solder to complete the joint. The cheaper end-feed fittings are simply metal sleeves and molten solder has to be fed into the joint from a length of solder wire.
Tools required to make soldered capillary joints are a means of cutting the tubing to length — a hacksaw or tube cutter — and of cleaning the end of burr. You’ll also need a blow torch, some wire wool or fine abrasive paper, some flux and — for end feed joints only — a roll of solder wire. Don’t overlook the fire risk when using a blow torch. Have a sheet of heat-resistant material handy to interpose between the capillary fitting and any flammable surface — a skirting board or a rafter for instance — that may be behind the working area.
This is the way to make a capillary joint using copper tubing. The rather different technique used with stainless steel tubing will be described later.
Cut the tube ends absolutely square and
remove all burrs as described earlier for making compression joints. Clean the outside of the tube ends and the inside of the capillary sleeve with either. Fine wire wool or with fine abrasive paper. Thorough cleanliness is the secret of success when making joints of this kind. Smear flux on the surfaces that you have cleaned.
Insert the tube ends into the capillary sleeve as far as the tube stops. With an integral ring joint all that remains to be done is to heat the sleeve gently and evenly with the flame of the blow torch. The solder will melt and run to fill the space between the tube end and the sleeve. The joint is complete when a bright ring of solder can be seen all around the mouth of the coupling.
When this occurs, wipe off excess flux and leave undisturbed until cool enough to touch.
With an end-feed fitting, preparation is exactly the same but, when the fitting has been heated, solder wire is applied to the mouth of the joint. This will melt and flow between pipe and fitting to make the joint. Once again the joint is complete when a ring of solder appears all round the mouth of the fitting.
It can sometimes be helpful to know roughly how much solder will be needed to complete an end-feed capillary joint. A 15mm joint is likely to need about 1/2in of solder wire, a 22mm joint about 3/4in and a 28mm joint about 1in. It is a good idea to bend over this amount of wire before you begin to make the joint. You will then have a good idea when it is almost complete.
Most soldered capillary fittings — couplings and tees for instance — have more than one joint. It is best to make all these joints at the same time. Where other joints of one fitting have to be made later then joints already made should be wrapped around with a damp cloth. This will prevent the solder from remelting.
Stainless steel tubing
Stainless steel tubing can be joined by the same capillary fittings that are used with copper tube but at least one manufacturer makes a range of stainless steel fittings for this purpose.
The tube ends are prepared in exactly the same way as the ends of copper tube but a special phosphoric acid flux — instead of the usual chloride based flux — must be used. This can burn the fingers so apply it with a brush or spatula.
When heating the joint apply the flame to the fitting only — not to the stainless steel tube. Remember that stainless steel does not conduct heat so readily as copper. Heat the fitting carefully, endeavouring to apply heat to the back as well as to the front. Your heat-resistant mat placed behind the fitting will help by reflecting the heat back.
When applying end-feed solder wire apply it to the mouth of the fitting in two or three places to make sure that the molten solder flows throughout the space between tube and fitting.
Exact fit is more important with capillary
fittings than with compression ones. Metric
size fittings cannot be used with existing
imperial size tube. However, conversion couplings — with the imperial size at one end and the metric size at the other — are freely available.
Bending copper tubing
When installing copper water supply and distribution pipes, changes of direction can be achieved by the use of the soldered capillary or compression bends that are included in every range of these fittings. However, a neater — and much cheaper — result can be obtained by bending the pipe itself.
You will find that the 15mm and 22mm copper tubes used in domestic plumbing can quite easily be bent by hand, over the knee. This, however, results in the pipe being deformed. The inside of the bend is wrinkled, the outside is flattened and the pipe becomes elliptical instead of circular in section.
By supporting the walls of the pipe as the bend is made this deformation can be avoided. This can be done with a bending machine or bending springs. Bending machines are expensive and it is best to hire one.
Bending springs support the walls of the tube internally. They can be used to achieve easy bends (a minimum radius of 40mm for 15mm tube and 60mm for 22mm tube). The spring — of the appropriate size for the tube that is to be bent — should be greased to facilitate withdrawal and inserted to the point at which the bend is to be made. Bend over the knee, overbending by a few degrees at first and then bringing the pipe back.
Insert a bar into the loop at the end of the spring, twist to reduce the spring’s diameter and pull to withdraw. Slight wrinkling on the inside of the bend can be dressed out afterwards with a hammer. Never attempt this before withdrawing the spring. If you do you will find the spring quite impossible to remove.
Watertight screwed joints
At one time it was the practice to make screwed joints used in plumbing systems watertight by coating strands of hemp with jointing compound and binding them around the male thread of the screwed joint.
This was messy and uncertain in its effect but it is still found in many older houses and is a useful technique. Nowadays, PTFE plastic thread sealing tape provides a cleaner and more effective way of making screwed joints watertight. This tape-can be purchased on reels from builders’ merchants or DIY shops.
To ensure a watertight joint bind the tape anti-clockwise three times round the male thread before screwing it home. This prevents the tape being pulled off. A screwed joint sealed with PTFE tape can easily be undone again when required.
The swivel tap connectors used to connect water supply pipes to the screwed tails of pillar taps and ball-valves are normally provided with a fibre washer that makes the connection watertight without other treatment.
Plastic tubing may be used in domestic plumbing for cold water supply and distribution and for waste pipes and drains. Certain types (CPVC and polybutylene) may also be used for hot water distribution and central heating, special fittings being available to allow connections to boilers and hot-water cylinders.
One of the most versatile of plastics is UPVC. Where UPVC pipes are used for cold water supply they are joined by solvent welding. For waste pipes they may be either solvent welded or connected by push-fit ring sealed joints. Often both methods are used in one system.
Polypropylene is sometimes used for drainage work as it stands up to hot and chemical wastes better than UPVC. Polypropylene pipes cannot be solvent welded.
CPVC pipes are solvent-welded in the same way as UPVC. Polybutylene cannot be solvent welded and is joined with special push-fit fittings or, if required, using conventional brass compression fittings.