Many plumbing textbooks begin with a study of the materials used by the plumber and the means by which pipes and fittings of these materials are joined together. It is the author’s opinion that, for the beginner at any rate, this is the wrong approach. The student of plumbing, whether he hopes to become a professional plumber or is ‘merely’ an intelligent householder, first needs to familiarise himself with the principles of water supply and drainage. Only when he has thoroughly mastered these principles should he attempt the practice by which they are put into effect.
Plumbing practice, so far as it relates to domestic water supply and drainage, consists of the means of manipulating pipework of different materials and connecting these pipes to others of the same or different material or to plumbing fittings such as taps, ball valves, cisterns and cylinders.
Materials used in plumbing installations today include copper and its alloys, stainless steel, galvanised steel and iron, lead and its alloys, pitch-fibre and a variety of plastics.
Copper is one of the most versatile and easily handled modern plumbing materials. It is used for water supply pipes, hot water storage cylinders and for waste drainage. Alloys of copper, brass and gunmetal are used for the manufacture of taps, stop-valves, ball-valves and indeed, all plumbing joints and fittings.
Copper tubing used for domestic water supply and central heating is supplied in ‘half hard’ and ‘dead soft’ temper. Half hard temper tubing is obtainable in straight lengths and is the kind generally used for above-ground water services. Dead soft temper copper tubing is sold in long coils and is particularly useful for underground service pipes where joints, potential points of leakage, are undesirable. Dead soft copper tubing is also used in microbore central heating as it can easily be threaded through and under floorboards to make for unobtrusive installation.
The commonest means of jointing copper tubing for domestic water supply and waste drainage are by the use of non-manipulative compression joints, manipulative compression joints or by means of soldered capillary joints. All these joints are easily made with a minimal tool kit and are suitable for both professional and amateur use.
Joints and fittings for use with copper tubing may be made either of brass or of gunmetal. Joints and fittings of the latter material are recommended in areas where the water supply has corrosive characteristics and the phenomenon known as ‘dezincification’ is liable to occur. Dezincification is a form of electrolytic corrosion which results in the zinc of the brass alloy dissolving away to produce a fitting, unchanged in external appearance, but totally without structural strength.
Non-manipulative compression joints and fittings
These provide the simplest, though not the least expensive, means of joining copper tubing and connecting to it fittings such as stop-cocks, taps and ball-valves.
A Type A compression joint comprises a joint body, a cap nut and a soft copper ring or ‘olive’. To connect a compression joint to one end of a length of copper tubing the procedure is as follows.
Cut the tube end square and remove all trace of internal and external burr. This operation can be done with a hacksaw and a file but, where a number of joints are to be made, the use of a wheel tube cutter, preferably incorporating a reamer to remove internal burr, will save time and ensure a squarely cut end every time.
Some manufacturers recommend that, in order to make the joint, the cap nut, followed by the olive, should be slipped separately over the pipe and this end thrust into the body of the joint as far as the pipe stop. Others say that there is no need to dismantle their joints before making them. Simply loosen the cap nut and push the tube end home. In either case the tube end must be pushed in to the pipe stop and the cap nut tightened. This action compresses the olive against the outer wall of the tube to make a watertight joint.
Tighten with the fingers and complete the tightening process with a spanner. Provided that a spanner, rather than a wrench, is used, it is virtually impossible to overtighten. Most professional plumbers smear a little boss white or other waterproofing compound over the tube end and the interior of the compression joint before making the joint. Although this should not be necessary it does accommodate any unevenness in the tube and ensures a watertight joint at the first attempt.
Manufacturers of Type ‘A’ compression joints publish illustrated catalogues of their products which show the very wide range of fittings available. Stop-cocks and drain-cocks are made with compression inlets and outlets for direct connection to pipes. There are also easy and elbow bends, equal and reducing tees for inserting branch pipe lines, fittings with compression inlets and cap and lining outlets for connection to taps and ball-valves and fittings with compression inlets and threaded outlets, male or female, for connection to cylinders, cisterns and pipes of materials other than copper.
Manipulative compression joints and fittings
These differ from Type A joints in that the tube end has to be ‘worked’ or manipulated and is itself an integral part of the completed joint.
To make a Type B joint the tube end must first be cut squarely and all burr removed as with a Type A joint. The cap nut must then be unscrewed from the joint and slipped over the tube end. After this has been done the tube end must be manipulated.
This is usually done by hammering in a steel drift to expand the tube end. However, one well-known make of Type B joint requires the tube end to be manipulated in a rather different way. A special ‘swaging tool’ is inserted into the pipe end and turned. Turning this tool forces a hard steel ball to make a ridge or ‘swage’ round the pipe end. The pipe is then placed against or into the body of the joint as the case may be and the cap nut screwed on and tightened. It is wise to apply boss white to the pipe end when making a Type B joint.
As can be seen, once the pipe end has been manipulated, the cap nut cannot be removed. This means that the pipe is much more positively secured than with a Type A joint. The joint cannot pull apart as a result of ground settlement or expansion of ice. For this reason Water Authorities usually insist upon the use of Type B joints for underground work. A disadvantage, which is probably not a serious one in most situations, is that the joint cannot be dismantled as easily as a Type A joint.
Soldered capillary joints and fittings
The effect of capillary action—the property of liquids that causes them to flow into any confined space between two solid surfaces-can be demonstrated by means of a simple experiment. Take two pieces of glass, separate them by about l ½ mm and dip their edges into a vessel filled with coloured water. The water will be observed to flow upwards to fill the space between the two sheets of glass.
Capillarity has its disadvantages. It is, for instance, the cause of rising damp in buildings. The plumber however can take advantage of it. The effectiveness of soldered capillary joints depends upon the fact that molten solder, like water, will flow to fill any confined space between two solid surfaces.
Soldered capillary joints and fittings are smaller, cheaper and less obtrusive than compression joints and fittings. They are scarcely more difficult to make though a blow torch is, of course, an essential.
There are two kinds of capillary joint-the integral ring and the end-feed. Integral ring capillary joints incorporate sufficient solder to make the joint.
Preparation of the tube end begins as with a compression joint. Cut the end dead square and remove all burr. Next clean the end of the tube, and the internal bore of the capillary fitting, thoroughly with steel wool or fine abrasive paper. Apply an approved flux to both these surfaces. Thrust the tube end into the fitting as far as the tube stop. Apply the flame of a blow torch, first to the pipe in the vicinity of the fitting and then to the fitting itself. The solder in the integral ring will melt and flow to fill the narrow space between tube and fitting. The joint is made when a bright ring of solder appears all round the mouth of the fitting. It should then be left undisturbed until cool enough to touch.
Solder wire is used to feed solder into the cheaper end-feed fittings. About Vim of wire is needed for a 15mm fitting, %in for a 22mm one and lin for a 28mm one. It can be helpful to bend this length of wire over before beginning the operation. Cut, clean and flux as before and apply the blow torch flame to the tube end and fitting. Feed in the solder when flux can be seen to be boiling at the mouth of the fitting. The joint is complete when all the bent over piece of wire has been melted and fed into the fitting and, as with an integral ring joint, when a ring of bright solder appears round the mouth of the fitting.
Where more than one joint is to be made to a fitting, as in a straight coupling or a tee connection, it is best if both or all joints can be made at the same time. If this is impossible a piece of damp cloth whould be wrapped round joints already made to prevent the solder in them from melting.
Always remember the fire risk when using a blow torch. Interpose a sheet of asbestos or a piece of fibreglass between the joint and any wooden, or plastic, surface in the vicinity.
Other jointing methods
Other means which may be used by the professional plumber for jointing copper tubing include silver or hard soldering and bronze welding. These methods involve the application of considerably more heat than can be obtained from a conventional blow lamp or blow torch. For bronze welding oxy-acetelene apparatus is required and the techniques involved are not considered suitable for a beginner’s guide.
Imperial sizes of copper tubes in common use in domestic plumbing are: 3/8in, Vir, %in, lin, Iviin, l^inand 2in. Metric equivalent sizes are: 12mm, 15mm, 22mm, 28mm, 35mm, 42mm and 54mm. These equivalents are not exact translations of Imperial into metric measurements. The reason for this is that Imperial measurements of copper tubing are of the internal diameter. Metric measurements are of the external diameter of the tube.
When connecting new metric tubing to existing Imperial sized tubing 12mm, 15mm, 28mm and 54mm compression joints can be used, without adaptation with 3/sin, Viin, lin and 2in tube. Adaptors are required for the connection of %in, l^in and Iviin Imperial tube to 22mm, 35mm and 42mm metric tubing. These adaptors are readily available.
Capillary joints demand a much more critical fit than compression joints and, where new metric tubing is to be connected to existing Imperial sized tubing by means of capillary joints, an adaptor should always be used. An alternative, where 3/8in, Viin, lin or 2in tubing is concerned, is to deal with any metric extension by using a compression joint for the actual connection between Imperial and metric tubing and then to continue the job using capillary joints.
Bending copper tubing
All manufacturers of compression and capillary joints and fittings include a variety of bends within their range of products. Easy bends can however be made in copper tubing either by hand or with the aid of a bending machine and use of this technique can provide a neater, and considerably cheaper, installation.
If a piece of copper tubing is simply bent over the knee it will be noted that the inside or throat of the bend is kinked and the outside or back is flattened while, at the bend, the tube will be elliptical instead of circular in section. To prevent this from occurring the walls of the tube must be supported as the bend is made.
One way of doing this is by means of a bending spring. Steel bending springs are made for all sizes of copper tube. They have an eyelet in the end into which a tommy bar can be inserted. Alternatively, where the bend is to be made in the middle of a length of pipe an extension rod can be hooked into this eyelet.
The spring should be greased to facilitate easy withdrawal and inserted into the tube to the point at which the bend is to be made. The tube is then bent over the knee, overbending by a few degrees at first and then bringing back to the required curve. To withdraw the spring insert a tommy bar into the eyelet, twist to reduce the diameter of the spring, and pull.
A bending machine provides an alternative means of bending copper tubing and will probably be preferred by the professional. The essential difference between spring and machine bending is the fact that in spring bending the walls of the tube are supported internally, while a bending machine provides external support.
Easy bends in small diameter copper tubing may be made cold. For sharper bends or for easy bends in large diameter pipe, sand or lead loading may be necessary to support the walls and the metal of the tube may need to be annealed-heated to a red heat to change the temper of the copper from half-hard to soft.
Stainless steel is widely accepted as a first class material for the manufacture of sinks and other kitchen equipment. Although stainless steel tubing has been available in this country for over a decade as an alternative to copper tubing it has not earned the popularity that it deserves.
Stainless steel tubing is obtainable in the same sizes as copper tubing. It can be used in any situation where copper could be used and in some situations where it would be unwise to use copper.
There is no such risk involved in the use of stainless steel. This material can be used in conjunction with copper tubing or, provided that it is not already rusting, old galvanised steel plumbing. It is therefore the obvious choice when extensions are planned for an existing galvanised steel plumbing system. Stainless steel, as a home product, has a relatively stable price that compares favourably with that of copper tubing.
Like copper tubing, stainless steel tubing may be joined with either Type A or Type B compression joints or by means of soldered capillary joints. There are however one or two points that should be noted when jointing stainless steel tubing. Although a wheel tube cutter can be used with stainless steel tubing this material is best cut with a high speed hacksaw blade having 32 teeth per inch. This is especially important if Type B compression fittings are to be used. A tube cutter will work harden the tube ends and make them liable to split when manipulated. Stainless steel is a harder material than copper. For this reason a little more pressure may be required when tightening the cap nut of a compression joint to ensure a watertight joint.
When using capillary fittings with stainless steel tube a phosphoric acid, not a chloride, based flux should be used. The supplier of the tubing should be able to suggest a suitable flux. The flux should be applied to the tube end and the interior of the fitting with a brush, not with the fingers. In making a capillary joint with stainless steel tubing a gentle flame from the blow torch should be applied to the fitting itself, not to the tube. As with copper tubing the joint is complete when a ring of bright solder appears round the mouth of the fitting.
Stainless steel tubing is less easily bent than copper tubing. Tubing of up to 22mm diameter can be bent using a bending machine. Spring bending is suitable for tubing of 15mm diameter or less.
Screwed iron and steel pipes and fittings
Because of their weight, clumsy appearance and the fact that they cannot be bent, screwed iron and steel tubing, usually protected against corrosion by galvanising, are rarely if ever used in new plumbing work today.
These materials were however in common use between about 1920 and 1940. It is not unusual to find pre-war suburban homes with hot and cold water systems wholly of galvanised steel—cold water storage cistern, hot water storage tank, flow and return pipes and distribution pipes. It may therefore be required for replacement or extension work. Pipes of this kind have threaded ends and are joined by means of the screwed fittings illustrated. To ensure watertight joints p.t.f.e. plastic thread sealing tape should be bound round the male thread before it is screwed home.
It not infrequently happens that the galvanised steel hot water storage tank of a hot water system constructed of this material fails through corrosion while the remainder of the system is still sound. In this event the temptation to replace the tank with a modern copper hot water storage cylinder should be resisted unless it is proposed, at the same time, to replace the galvanised steel tubing that comprises the remainder of the system with either copper or stainless steel tubing. The risk of electrolytic corrosion is even greater in hot water systems than in cold systems.
The metrication of iron and steel tubing has resulted in rather less confusion than has the metrication of copper and stainless steel tubing. Measurements are still of the internal diameter.
For all practical purposes there is no change between the sizes of Imperial iron and steel tubing and their metric equivalents. The British Standard Pipe thread form has now been accepted internationally and its dimensions will not change. This, of course, relates to the tails of taps and ball valves as well as to iron pipe fittings.
Lead is the traditional plumbing material. It is, of course, from its Latin name that the word plumbing is derived. Its expense, and the expertise and experience that is needed to handle it efficiently, ensures that it is never nowadays used for new hot or cold water services or drainage. There are however a great many lead, or partially lead, plumbing systems in existence. The professional plumber at least, must know how to cope with lead pipe for replacement and maintenance work.
Lead pipes are joined together by means of a wiped soldered joint. In the introduction it was stated that the technique of making such a joint is far easier to describe that to put into practice. The beginner will probably need to make several attempts before he produces a wiped soldered joint of which he can feel proud. He may console himself with the thought that it is a skill, like riding a bicycle, which, once acquired, is never lost. Before examining the technique, we should look at the properties of solder.
Solder is an alloy of lead and tin, and a small percentage of antimony. Its value lies in the fact that it has a lower melting point that any of the elements of which it is composed. Hence the fact that it can be used to join lead pipe without the risk of the lead itself softening and becoming deformed. Solder used with the soldered capillary joints discussed earlier in this post has a relatively high percentage of tin and a low melting point-between 170 and 190°C or 340 and 370°F. Plumber’s wiping solder on the other hand contains roughly two parts of lead to one of tin and has an appreciably higher melting point-230°C or 440°F.
Careful preparation of the pipe ends is the first important step in the making of a good wiped soldered joint. Ends should be cut squarely and cleaned of all burr. A socket is then formed in one pipe in a tanpin, or hardwood cone. The exterjial edge, or ‘arris’, of this opened-out end is then rasped away. The other pipe end is formed into a spigot by rasping to the angle of taper of the tanpin. This will ensure that it fits closely into the socket prepared in the other pipe end.
To limit the extent of the completed joint each pipe end is now coated with tarnish or plumber’s black, to which molten solder will not adhere. Mark the limit of the joint on both spigot and socket ends and, with a shavehook, shave away the tarnish and the surface coating of lead oxide from the area of the joint, leaving bright, bare metal exposed. The cleaned surfaces must immediately be protected from further oxidation by smearing with tallow. Assemble the joint and fix firmly for wiping.
There may still be some traditional plumbers who make wiped joints with a solder pot and ladle, splashing molten solder onto upright joints with a splash stick and moulding into shape with a wiping cloth. Most modern plumbers prefer to use the solder stick method which is easier, safer and can produce just as satisfactory results.
The flame of a blow torch is applied to the lead pipe on each side of the joint, slowly traversing to and fro until the lead has reached a temperature above that of the melting point of solder. Rub the solder stick lightly onto the shaved surface of the lead pipe so that it ‘tins’ the entire surface and runs, by capillary attraction, into the confined space between the spigot and socket of the joint.
As more heat is applied the solder stick will soften and blobs of solder will be released. These must be built up round the joint with the moleskin wiping cloth to a neat finish.
The length of a wiped soldered joint will depend upon the sizes of the pipes being joined.
As with galvanised iron and steel tubing, lead tubing is still designated by its internal diameter and there is no change, for all practical purposes, between the sizes of Imperial lead tubing and their metric equivalents.
The wiped soldered joint described is most likely to be needed in connection with the replacement of a burst or leaking length of existing lead pipework. This should be a relatively rare occurrence.
What the modern plumber is more likely to need is a means of connecting new copper or stainless steel tubing to existing lead pipe. This situation frequently arises in modernisation and improvement work. An obsolete and leaking lead plumbing system has been ripped out and a new copper or stainless steel system is to be installed. The first task is to connect copper tubing to a cut-off length of lead tubing projecting from the floor boards.
All manufacturers of compression and capillary joints and fittings include lead-to-copper connectors within their range of products. There is no difficulty in connecting the copper end of the connector to the copper or stainless steel tube. The lead end has to be connected to the lead tube by means of a wiped soldered joint similar to that described above. The projecting end of lead tube will form the ‘socket’ of the new joint. It must be opened up with a tanpin, rasped and cleaned as though another length of lead pipe were to be connected to it.
The lead end of the lead-to-copper union must now be prepared. Its tail must be thoroughly scored with a medium cut file to remove the dull coating of chemical impurities arising from oxidation. The filed portion must be lightly smeared with tallow and plumber’s black applied to the other end of the fitting to mark the limit of the joint.
The scored end of the union must then be ‘tinned’. This means covering with a coat of fine general purpose solder, composed of equal parts of lead and tin. The solder is best applied to the tail of the union with a large copper bit. When the union has been tinned its end is placed into the socket of the lead pipe and secured with wooden splints. The wiped soldered joint is then made as previously described.
A simpler copper to lead connection can be made with a cup-and-cone joint. This is acceptable for waste pipes and gas fittings but cannot be used for pipes carrying water under pressure. The end of the lead pipe is belled out by driving in a hardwood cone or turn-pin until the spigot end of the union can be accommodated to a depth equal to about half of its diameter. The spigot end of the union is rasped and tinned and fixed firmly into the lead socket. Fine solder is then run into the cup, the space between the union spigot and the lead socket, to fill it.
Polythene may be used in plumbing for cold water storage cisterns and feed and expansion tanks. It may also be used for cold water supply and distribution pipes and was one of the first plastics to be used for this purpose. Polythene tubing is obtainable in long coils. It can easily be connected to copper tubing and has a built-in resistance to frost.
Its disadvantages are its thick, clumsy appearance and its tendency to sag which necessitates continuous support on horizontal runs. It cannot be used for hot water under pressure but is suitable for waste pipes taking warm wastes from baths, sinks and basins. Its chief value is as an easy and relatively cheap means of taking an underground water supply to a point distant from the home. It can be used to provide a garage supply or to supply a stand-tap at the end of a large garden.
The long lengths in which it is obtainable eliminate underground joints and it can be brought above the surface of the ground to supply a stand-tap without special frost precautions being taken. Polythene is a poor conductor or heat and cold and will provide a considerable measure of frost resistance. If the water in a polythene pipe does freeze the pipe will not burst. Polythene has sufficient resilience to accommodate the expansion of the ice and will revert to its original size when the ice thaws. These considerations make polythene tubing extremely valuable to, for instance, the proprietor of a caravan or camping site who must take a water supply to stand-pipes at various points throughout the site.
Polythene tubing is joined by non-manipulative compression joints and fittings similar to those used with copper tubing. Because polythene is a relatively soft material, a metal insert, provided by the manufacturer of the fitting, must be fitted into the tube end to prevent collapse when the cap-nut is tightened. Unscrew the cap-nut of the compression joint and slip it, followed by the olive, over the end of the tube. Push the metal insert into the end of the tube. Insert the tube end into the body of the fitting as far as the tube stop and tighten up the cap-nut. Tighten as far as possible with the fingers and then give a further one and a half to two turns with a spanner.
Polythene has not, at the time of writing, been metricated. Because of the thickness of this material it is usually necessary to use a compression fitting one size larger than the nominal size of the equivalent copper tubing. V4in polythene tubing will probably require a 22mm fitting. It is however wise to take a sample of the tube along to the supplier to make sure that the right size of fitting is purchased.
Polythene tubing can be bent cold to easy bends but will revert to shape unless firmly secured. Permanent bends may be made by softening the length of pipe by immersion for ten minutes in water that is kept boiling or by very gently playing the flame of a blow torch along it.
Unplasticised polyvinyl chloride
Unplasticised polyvinyl chloride is the most versatile of modern plastic materials so far as the plumber is concerned. Pipes of this material may be used for cold water supply, for above and underground drainage and for roof drainage. It is light, tough and easily handled and joined.
P.V.C. cannot be used for hot water under pressure. For this reason there are two, nominally cold water supply pipes which should never be of P.V.C. These are the cold supply pipe from the cold water storage cistern to the hot water cylinder and the cold supply pipe from the feed and expansion system of an indirect hot water system. Water in these pipes can become very hot at times and, for this reason, metal pipes should always be used.
P.V.C. tubing can be joined either by solvent welding or by ring seal jointing. Solvent welding is always used for cold water supply pipes. For waste and drainage pipes a mixture of the two methods is often used; solvent welding for the small diameter waste pipes and for the connection of junctions and fittings, ring seal jointing for long lengths of the larger diameter stack and drain pipes.
Manufacturers supply fixing instructions which vary slightly with each brand. The following instructions apply to the fixing of Osmflow p.v.c. water supply and distribution pipes.
Cut the pipe to the required length with a hacksaw or other fine toothed saw. Make sure that the pipe end is square and clean off any swarf or burr. With a fine rasp or coarse file chamfer the pipe end to an angle of approximately 15.
Roughen the external surface of the pipe end and the internal surface of the socket with a medium grade abrasive paper. Do not use steel wool as this will polish the surfaces.
Apply a coat of approved spirit cleaner and degreaser to the inside of the socket and to the pipe end for at least the distance that it will fit into the socket.
Wipe off with clean tissue and apply to both surfaces an even coat of solvent cement. Stroke the cement along, and not round, the surfaces. Thrust pipe end into socket, twist and hold in position for a few seconds. The joint may be handled after two to three minutes but should not be put into operational use for about 24 hours.
Key Terrain Ltd. give similar instructions with their p.v.c. water supply and distribution system but say that the pipe end should not be twisted when thrust into the socket. They also suggest that a thicker coat of solvent cement should be applied to the pipe end than to the interior of the socket.
Marley Extrusions Ltd., in their extremely well illustrated instructions for pipework installation, give rather different advice in connection with the solvent welding of their above ground drainage systems.
The pipe end is cut square, cleaned and degreased in the same way as described earlier but it is not chamfered to an angle. They suggest that, after application of solvent cement to pipe end and socket interior, the pipe should be thrust into the socket ‘with a slight twisting motion’ and held in position for about 15 seconds.
A 4m length of p.v.c. pipe will expand by over 13mm when subjected to an increase in temperature of 39°C. For this reason, where a total straight length of waste pipe exceeds 1.8m in length, an expansion coupling should be introduced at 1.8m intervals. The Marley expansion coupling has a solvent weld connection at one end and a ring seal joint at the other. An insertion mark made 57mm from the pipe end ensures that accommodation for expansion is provided.
An advantage of ring seal jointing is the facility that it provides for the accommodation of thermal movement due to the passage of hot and cold water through waste and drain pipes. Preparation for ring seal jointing is similar to that for solvent welding. A fine toothed saw or hacksaw must be used to cut the pipe end absolutely square. Draw a line round the cut end of the pipe 10mm from the end and chamfer back to this line with a rasp or special shaping tool. Insert the pipe into the socket and mark the insertion depth with a pencil. Make another mark 10mm nearer to the pipe end than the first mark. It is to this second mark that the pipe end will finally be inserted, thus leaving 10mm for expansion.
Clean the recess within the pipe socket and insert the sealing ring. Lubricate the pipe end with a small amount of petroleum jelly and push the end firmly home into the socket past the joint ring. Adjust the pipe position so that the insertion depth mark is level with the edge of the socket.
Manufacturers provide a variety of means by which p.v.c. water, waste and drain pipes may be connected to taps and ball-valves, copper or galvanised steel tubing and to stoneware and iron drainage systems.
Polypropylene tubing resembles p.v.c. in many respects. It may be encountered in domestic drainage work but is of greatest value for the drainage of high temperature and chemical wastes from industrial and commercial premises.
The important point of difference between polypropylene and p.v.c. is the fact that the former cannot be joined by solvent welding. Ring seal joints must be used in all situations.
Expanded polystyrene is used in plumbing as an extremely valuable lagging material. It is obtainable in pipe lagging units which can be fitted round pipes during or subsequent to installation. Tank lagging sets for cold water storage cisterns are also available. Despite its ‘porous’ appearance it does not, in fact absorb water in any appreciable amount. It can therefore be used to protect underground pipes when required.
Fire risk should always be borne in mind when expanded polystyrene is used. It can burn, giving off dense and potentially lethal fumes.
Pitch fibre pipes
Pitch fibre pipes are sometimes used for above-ground waste and soil stacks. Their most common use however is for underground drainage work.
The simplest method of jointing is undoubtedly the snap ring joint. The snap ring is placed over the end of the pipe, care being taken to ensure that the ring is square to the axis of the pipe and that its flat surface is in contact with the pipe. The coupling is then pushed home over the ring and pipe end so as to force the ring to roll along the pipe. Due to the shape of the ring’s section it is compressed and jumps into its final position. This can be distinctly felt and is an indication of a sound joint.
Pitch fibre pipe can be cut with an ordinary wood saw. Keeping the blade lubricated with water will prevent clogging and speed the operation. As with p.v.c. waste and drain pipes a variety of means are provided for the connection of pitch fibre pipes to pipes and fittings of other materials.