Plumbing installations

Introduction

This chapter covers standard plumbing installations. Mechanical heating/cooling/refrigeration systems, and ventilation and air conditioning systems, are more specialized forms of mechanical engineering and are generally carried out by specially trained tradesmen. Examples for these systems will not be given. However, the principles of the plumbing examples can be applied to these other systems, bearing in mind the differences in wage costs and the need for specialized tools and plant, especially for handling bulky or heavy items. 

The SMM7 sections are: rainwater pipework/gutters; foul water drainage above ground; pipelines; pipeline ancillaries; and sanitary appliances/equipment. 

All-in rates for pipe

Pipe is available in a bewildering variety of materials and types. For the plumber, plastics, metal and composition materials are the most common. In these materials, pipes are manufactured to carry hot and cold water; other liquids, including those that are corrosive, flammable, toxic, etc.; gases; foul water, rain water and waste water; and so on. Such pipes share certain features which make it possible to treat them as a single class for measurement, and also allow us to generalize in the explanation of how to determine all-in rates. 

Pipe is supplied in lengths or coils, rigid or brittle materials being in lengths and flexible materials being in coils. The most common length is 6 m. However, some pipe is supplied in shorter or longer lengths, especially where the joint is formed as part of the pipe, as in PVC or cast iron soil pipe with spigot and socket joints. Cast iron pipe and gutters are still supplied in imperial lengths of 6 feet. Variety of lengths for pipe with integral sockets (say 1, 2, 3 and 4 m) reduces waste, because every cut produces a length with a joint and another length without a joint! 

Coils of 25, 50, 100 or 150 m are common, but some pipe is supplied in 30 m or even 60 m coils. The coil length is dictated as much by what the plumber wants to keep in stock as by old traditional manufacturing processes. For example, it might not have been possible to extrude more than 30 m of a particular pipe in one operation, and therefore it became standard practice to supply in coils of that length. The pipe must inevitably be cut to length. The shorter are the cut lengths, the greater is the labour, the fewer are the joints in the running length and, depending on the rigidity of the pipe and the appliances served, the fewer are the fastenings to hold the pipe in place. 

Pipe material varies in its bending ability as follows: 

• Bends can be easily made, e.g. in polyethylene and polybutylene water pipe (although of large radius)
• Bends can be made with apparatus, e.g. in half hard copper pipe (BS 2871 Table X) for hot and cold water supply, using springs or a light bending machine 
• Bends cannot be made and elbows or bent couplings have to be used, e.g. in cast iron pipe, uPVC soil pipe or hard thin wall copper pipe (BS 2871 Table Z). 

The material is always fully specified so that identification is positive. 

There is generally a standard method of fixing the pipe in position. Non-standard fixings must be fully specified in the bill item or preamble. The background to which the pipe is fixed is also given. Backgrounds are tabulated in the general rules to SMM7, 8.3(a) to (e). 

Joints

Although joints in the running length are deemed to be included, there is a standard method of jointing for each type of pipe in each situation and the cost of labour and materials used for each must be taken into account in the pricing of the running lengths. 

Joints occur of course at fittings, i.e. junctions, bends, elbows, valves, etc., and where pipe is connected to sanitary fittings, tankage, etc. In every instance there is a standard method of forming these joints and connections and they are measured separately from the pipe, although some may be included with the apparatus. 

Here it may be as well to define the two types of joint that a plumber can make. A coupling is designed to join pipe to pipe only. A connection is used to join pipe to sanitary fittings, tanks, cylinders, etc. Both tradesmen and suppliers now use either term indiscriminately. The term 'joint' will be used in this text to mean either type. 

When making joints the tradesman will use very small (per joint) amounts of general materials. For example, capillary joints on copper pipework require steel wool to clean the pipe, flux to assist in making the solder flow into the whole joint, and fuel to provide heat for the blow torch or clamps. Capillary joints may or may not have an integral solder ring, and if not then solder must be allowed for. Compression joints will require either jointing compound or PTFE tape to ensure a water/gas tight joint. The ring sealed push fit joints on PVC waste pipe require a lubricant. The threaded joints in galvanized steel pipework require hemp yarn and jointing compound or PTFE tape. Joints in spigot and socketed cast iron pipe require gaskin, molten lead and fuel for the furnace. The list goes on and on. 

In practically every instance very small amounts of material are used which would be tedious to quantify for every joint. The usual practice is to make a monetary allowance for items like PTFE tape, jointing compound, etc., either in the preliminary works bill or as a small percentage addition at the time of building up the rate. Easily quantifiable and more expensive materials such as solder in end feed joints, or lead and yarn for cast iron soil pipes, are actually quantified and priced when building up the rate for joints of that kind. 

SMM7 has recognized that joints are important to the estimator by classifying couplings and connections as having one, two, three or more ends. However, it has made costing difficult for the estimator by lumping together all fittings up to and including 65 mm diameter in one item. (See, for example, rule 2.3.* in Section R on disposal systems.) The difference in cost between a brass/gunmetal 15 mm tee and one of 28 mm is quite significant. More of this is illustrated in the examples which follow. 

Special tools 

The plumber requires many special tools besides spanners, grips, etc.: for example, blow torches (now generally fuelled with butane or propane), pipe bending machines, pipe threading machines, testing equipment for boiler flues and gas installations and so on. It would not be sensible to attempt to allocate the costs for these tools over each individual item in the bill of quantities. The best solution is to put the cost into the preliminaries bill. Fuel in connection with any of these tools or small plant items might be included here rather than in the rates. The basis for the calculation of the amount of fuel is the general size of the contract and knowledge of fuel consumption on previous contracts. 

Labour costs and outputs

In Chapter 2 it was noted that plumbers are paid at a higher rate than other operatives. Thus all-in hourly rates have to be established for this section of work for the various grades of skilled, semi-skilled and unskilled workers. Plumbers are generally classified as technical, advanced and trained; the first two grades carry out various degrees of supervision. The plumber generally operates with a mate, who may be a lower or similar grade of plumber, or even an unskilled worker or an apprentice. Wages for plumbers, apprentices and mates are generally agreed by the Joint Industry Board for the Plumbing and Mechanical Engineering Services Industry. 

The first thing to consider is whether or not the labour constants used are for one craft operative working on his own (this is rare), for one craft operative working in a gang, or for a gang. If the constants are for a gang then the composition of the gang must be known, e.g. two plumbers, a plumber and an apprentice, two plumbers and a labourer, and so on. 

Next the cost of this labour has to be considered. This is best illustrated with examples. To set the scene it will be assumed that all-in hourly rates for the following operatives have been calculated: 

Plumbers:     technical                  £11.90 

                     advanced                  £10.65 

                     trained                      £10.05 

Apprentices: third                           £5.85 

      year 

Now, a single plumber is costed out per hour at his particular rate. For two plumbers in a gang, the gang is costed out as the sum of the individual rates. However, if the constants are for one plumber then the average rate of the individual rates is used. For example: 

                                                                                    Gang rate     Individual rate

1 plumber                                                                        -                    As grade

2 plumbers, 1 advanced, 1 trained                                £20.70              £10.35

2 plumbers as above and a 3rd year apprentice            £26.55             £13.28 

It will be noticed that in the calculation of the third individual rate, the contribution made by the apprentice to the gang's work is not included; the gang rate is divided by the number of qualified plumbers. This practice of ignoring the apprentice's contribution is common among estimators. Some do include such a contribution; however, it cannot be equivalent to a full craft operative. First of all, apprentices generally do not work as long a day as craft operatives. A third year plumbing apprentice only works 80 per cent of the hours of a plumber. Second, apprentices are allowed time off to attend technical college. Third, they cannot be as productive simply because they are still learning the craft and require guidance. Finally, their training is given by the craft operative(s) and this will slow the operative down. On balance, if apprentices are included in a squad it is probably best to ignore their contribution to production.
Rates used in the examples in this chapter are based on a gang of one advanced and one trained plumber, costing £20.70 per hour total. All constants given in the tables and elsewhere are based on output per craft operative working in a gang and so will be costed at the average rate of £10.35 per hour.

Copper pipework and fittings 
Table 1 shows ranges of outputs for copper pipework and fittings. The outputs have been abstracted from a variety of sources and reveal the diversity of opinion common among estimators. There has to be an explanation for these differences. The variable attributable to labour factors has been well rehearsed elsewhere in the text. This section deals with those factors attributable to trade practice and to specification.

Variations in pipework installations 
Take, for example, a pipe run along a wall in a warehouse or factory. There will be an uninterrupted flow of work. The operatives will snap a chalk line on the background; fasten clips to the background and mount the pipe in the clips; make joints in the running length as they proceed; and finally tighten the clips. The question of what type of joint is made will be discussed later. The only cutting will be at the ends. The plumber can reasonably be expected to erect better than 5 m per hour in these circumstances.
By contrast, take the situation where the pipe is being erected in the toilet blocks in the same warehouse or factory. The first lengths erected during the plumber's roughing stage will present slightly more difficulty due to the restrictions on space. Further time will be required to set out tees to sanitary fittings. The pipe connecting the plumber's roughing to the sanitary fittings will be even more difficult. There will be many made bends which, although measurable and priced separately, will require the plumber to take more time cutting pipe to the correct length. There will also be

proportionately more cutting to length than in any other situation. Moreover, there will be work in confined spaces and under and around the sanitary fittings. Horizontal runs of plastic pipework require more supports than the equivalent runs of metal pipework. 

Fittings 

Although two European standards (EN 1254-1 1998 and EN1254-21998) have been issued, BS 864 is, at the time of writing, still current for capillary and compression fittings suitable for the copper pipe under discussion. Two kinds of capillary fitting are manufactured, as well as two kinds of compression fitting. With both kinds of fitting there are many variations. 

The first type of capillary fitting has a solder ring incorporated by the manufacturer. If a flux is used which cleans the pipe, fittings can be pushed onto the pipe and heat applied for a fast joint. It is hard to believe that it takes 12 minutes to form such a joint between two straight lengths of pipe. However, it must be remembered that the plumber is expected to carry out such tasks for 8 hours a day, 5 days a week - and to plan ahead for the next joint! 

The second kind of capillary fitting has no solder in it. The pipe is smeared with flux (which again can be a self-cleaning flux), the fitting is pushed onto the pipe and heat is applied. A stick of solder must then be applied to each end of the fitting and allowed to melt and to be drawn into the joint. This is a much more skillful operation; it is easy to put in too little solder and have a joint that is leaky or weak under pressure, or to put in too much solder and allow it to flow into the pipe and cause an obstruction. The latter is obviously expensive in its use of solder and both are expensive when they cause problems for the contractor which have to be put right! In this instance, the time of 12-15 minutes per joint seems quite fair. 

The two types of compression joint are described as type A, non-manipulative, and type B, manipulative. Manipulative means that the ends of the pipes to which the fitting is attached are worked to a special shape which makes the joint mechanically sound and pressure tight. Non-manipulative means that the fitting has been designed to be mechanically sound and pressure tight without the need to do anything to the pipe. 

Polybutylene hot and cold water piping and fittings 

Systems specified in bills of quantities will generally be required to comply with BS 7291. 

Several manufacturers now supply both polybutylene piping suitable for the full range of water services - hot and cold supply and central heating — and in a range of sizes from 10 mm to 28 mm outside diameter, the same as copper pipe. This is important as the pipe can be substituted directly for copper pipe work in renovation works without the need to change the connections at tanks, cylinders and appliances. Early versions of the pipe suffered from the ingress of oxygen through the pipe wall which was detrimental to appliances in certain circumstances, for example central heating systems and especially sealed, pressurized systems. Most manufacturers can now supply a version with an oxygen barrier extruded into the wall of the pipe. 

Purpose designed push fit fittings are also made as part of each manufacturer's system. Generally, the wall of the pipe requires support at each fitting and this is given by the insertion of a shouldered liner into the end of the pipe before pushing it home. Various methods have been developed for allowing the fitting to be taken apart, some involve destruction of the grab ring if a new joint is to be made on the pipe; others allow the joint components to be reused for a limited number of times, sometimes using a special tool. Of course, alloy, non-manipulative, compression fittings can be used to join the lengths of pipe and as connections at appliances, tanks and cylinders. Support for the pipe wall becomes even more important when using compression joints. The pipe cannot be formed for use with manipulative fittings and of course capillary fittings cannot be used. 

Push fit fittings are all made on the same principle. They incorporate an 'O' ring seal and a `grab' ring. The 'O' ring seal is fairly obvious. When the pipe is pushed into the fitting it is pushed past the seal first which is squeezed between the pipe and the body of the fitting making a water tight seal. These seals have been used for half a century on soil waste and ventilation piping. With the 'O' ring seal there is no need for jointing tape or compound, indeed the use of compounds could damage the 'O' ring and the use of tape would prevent the pipe being pushed home into the fitting both resulting in leaks. The pipe is next pushed past the 'grab' ring, generally made of stainless steel. The ring fits round the pipe to be joined but has teeth on the internal edge past which the pipe has to be pushed quite firmly. These teeth point towards the body of the fitting and once the pipe is pushed past them they act like barbs and will not allow the pipe to be pulled back out. So strong is the grip of these barbs that bursting pressures on the joints similar to conventional compression and capillary fittings can be achieved. 

A word of warning to students and the inexperienced. Do not push your finger into one of these joints. It may slide past the grab ring easily enough but you may find yourself with a cut finger or one which is stuck in the fitting and requiring surgery to have the fitting removed. 

Various methods are employed to keep the components of the fittings together. Some manufacturers have a threaded nut over the ends of the fitting through which the pipe ends pass before encountering the seals and grab rings. To take the joint apart, the nut is unscrewed and screwed up again to remake the joint. Others use a captive nut with a quick release device on the grab ring actuated with a special tool. All joints incorporate washers and spacers to keep the seal and grab ring in their respective position within the joint. Generally, grab rings and 'O' rings remain intact each time the joint is taken apart but if the pipe end has to be altered in some way the 'O' ring can be reused unless damaged but the grab ring is destroyed and has to be replaced. All these items are sold separately by the manufacturers. 

Bends are easily made in the flexible plastic piping but refuse to stay put unless restrained. This is not a problem where the pipe is laced through joists or stud work but if laid loose over, say, a sub-floor, etc. a former has to be used or the pipe will simply take up the largest radius possible and may encroach into space for other services or components. With the use of formers, the bends are easily made without deforming the pipe cross-section down to radii of approximately 4-5 pipe diameters. The formers are comparatively expensive - much more than a made joint in copper pipe so their use is restricted to those situations where the natural self-positioning of the pipe has to be curbed. They generally have holes for screw fastening to a substrate. Elbows or knuckle bends could be used instead but a made bend is preferable as it does not restrict flow through the pipe. 

Any type of pipe clip which can be used with copper pipe can be used with polybutylene pipe but those comprising a metal band are best avoided as cyclical thermal movement of the pipe in the clip can result in the metal cutting through the pipe wall! Snap-in plastic clips or plastic saddles are preferred. 

The pipe is available in cut lengths generally of 3, 4 and 6 metres and in coils of anything up to 100 metres. Whichever length is supplied, the pipe has the same flexibility and this flexibility is promoted by the manufacturers as of particular advantage in running the pipe in confined spaces or through multiple timbers as in joisted floors or timber partitions. In particular, holes in these timbers do need to be accurately aligned in any way because of the flexibility of the pipe. The push fit joints are also promoted as being a 'time saver' and therefore a cost cutter. This is very true. Wet the end of the pipe with saliva (proprietary lubricant is available - at a cost) and push it into the fitting. Done quicker than it can be explained. Nor are there any ancillary materials used - joint tape or compund, fuel for blow torches, etc. The basic materials are more expensive than the equivalent copper pipe and alloy fittings but the labour required is much reduced. 

Table 2 gives labour outputs for running pipe in various situations and for the mounting of various standard fittings. 

Copper pipe of any grade can be used with these push fit fittings for two reasons. First, the outside diameter of both copper and polybutylene pipe is the same and second, the stainless steel grab rings will dig into and grip the soft copper pipe quite securely. These fittings cannot be used with chromium plated pipe or stainless steel pipe as a sure grip cannot be guaranteed on these harder surfaces.
The plastic push fit fittings are generally more expensive than the equivalent brass compression fittings and dearer still than capillary fittings. However, where DZR (dezincification resistant) fittings have to be used, plastic push fit fittings may turn out to be more economical especially when connection times are taken into account.
There does not appear to be any authoritative set of labour constants for plastic pipe with push fit joints. When contacted, several manufacturers were unwilling to give any figures even within a wide range of outputs per fitting, etc. One or two, however, claimed that output was about a third of that for copper pipe and fittings. I would regard this with some caution as fixing pipe is not dependent on how easy it is to joint! The general procedure for fixing pipe has still to be followed and will take exactly the same time whether one is fixing plastic, copper or any other pipe of the same diameter but taking into account the mass and jointing in the running length. So comparing Table 14.2 with Table 14.1 the reader will see that while outputs for fixing pipe remain the same, only those fittings which are wholly push fit have a reduced output.
 Examples of rates for plastics hot and cold water pipe and fittings are given later in the chapter.