CHAPTER VIII THE Burtpinc—Its SAnrrary FITTINGS AND (Part 7)

owing to the fact that the grating cannot accumulate a coating of grease or soap curd and so cause an overflow of dirty waste or bath water over the surround- ing ground—a very likely occurrence in autumn when leaves of trees are falling freely to complete the blockage. It uses slightly more pipe but there is a saving in labour with the brick on edge and rendered dishing to the gully top. Grease Traps. A third method is to use a grease trap. Grease traps are things to be avoided wherever possible and are not necessary for a private house. For hotels, clubs, or any places where exception- ally large quantities of greasy water are discharged, grease traps are practically a necessity, as the grease, in cooling, would tend to form a coating on the inside of the drain and so gradually reduce its diameter. They are also very desirable if the house is a rural one with its own sewage purification plant. There are two types, (1) those in which the grease is removed by hand, and (2) those in which it is broken up by a powerful flush of water and washed through the drain in its solid state. They will be dealt with under the heading of drainage, as they are only desirable in special cases. Foot of Soil-pipe. Soil-pipes should be directly connected to the drain without the intervention of any trap other than those at the outlets of the closets. The method of making the con- nection depends upon the materials of which the soil-pipe and drain are composed. Thus, if the drain be of cast iron and the soil-pipe lead, the foot of the latter would be strengthened by means of a brass, copper or gunmetal ferrule or thimble, and a caulked lead joint made to the junction of the two, as shown at A in Fig. 299. If both soil-pipe and drain be of iron, the ordinary caulked lead joint would be used, as shown at B in the same illustration. If, however, the drain be of stoneware, with a lead soil-pipe, the joint would be made with the help of a ferrule, using cement mortar or bitumen instead of caulked lead. The pouring of molten lead into the socket would split it to pieces and, even if lead wool be used, the caulking would split the socket. The joint for this case is shown at C in Fig. 800. If the soil-pipe be of iron and the drain of stoneware, a cement or bitumen joint is all that is necessary, as at D. The connection between a copper soil-pipe and an iron or stone- ware drain is made by using a standard fitting for diameters up to 2 in., and a brass or copper ferrule bronze welded to the tube 292 THE BUILDING—ITS SANITARY FITTINGS, ETC. for the larger sizes, the joint being then completed as in the case of lead soil-pipes. , It will be realised that the method, already described, of carrying down the waste pipes from baths, lavatories, sinks, etc., on the outside of buildings to gullies at ground level, before connecting them to the drains which take the discharge from soil-pipes, tends to make the buildings unsightly; especially is this so with lofty hotels, equipped with a basin in each bedroom and a generous allowance of water-closets, bathrooms and lavatories. In con- sequence, some changes are taking place. Internal Ducts for Soil and Waste Pipes. First, there is a ten- dency, in the design of large buildings, to collect all vertical pipes in one or more vertical shafts, erected as part of the main structure, means of access for inspection and repair being provided at each floor level. Besides improving the external appearance of the building this method lessens the risk of freezing of waste ipes. ” “‘One-pipe” Plumbing. Secondly, and of much greater import- | ance, there is a tendency to adopt what is known as the “ one-pipe”’ system, which has already been mentioned in this chapter. In this system the same vertical main pipe is made to serve as a soil-pipe and as a main waste pipe from baths, lavatories, ete.; the main pipe is, in fact, an extension of the drain up the wall of the building—most usually, but not necessarily, inside the wall of the building, as described above. Similarly one ventilation pipe will serve to ventilate fittings of all kinds—water-closets, baths, lavatories, etc. Strictly therefore there are two pipes in the “ one- pipe system”, a main waste pipe and a ventilation pipe, in addition to rainwater down pipes. The system is in general use in the United States of America, where buildings are, generally speaking, higher than in this coun- try. It is now coming into use in this country, being provided for in the by-laws of the London County Council and in the Model By-Laws, whose lead has now been followed by the by-laws of many local authorities up and down the country, particularly in the urban area. The system obviously is likely to reduce cost of construction, and of maintenance, in buildings of some size, though perhaps not in the case of small houses, unless the sanitary compartments in them are very compactly arranged. Further advantages are that the main is kept constantly flushed, that the alkalis of soapy waste water will neutralise the acid character of closet discharges and so diminish corrosion, and that unhygienic, greasy gullies are THE BUILDING—ITS SANITARY FITTINGS, ETC. 298 avoided. On the other hand, we have lost what was previously referred to as the first line of defence against the passage of drain air into bathrooms, kitchens and even bedrooms, and the trap in the fitting is the only barrier to the passage of foul air from the soil-pipe. Where the one-pipe system is in use it is therefore doubly im- portant that all traps shall have an ample water seal and that they shall be protected from siphonage by being of the anti-siphonic type, or fitted with anti-siphonage pipes leading to the main ventilation pipe; it is also most important that the plumbing generaHy shall be the best possible. Fig. 301 shows the general arrangement and a particular point to be noticed is the treatment of the ground floor. If the building is a high one it is possible that synchronising discharges of several closets may cause the lower part of the main waste pipe to stand full of water for some height, the underground drain not being able to carry it away fast enough. If any fitting, such as a bath or lavatory basin, were below the level of the top of this standing water, and were connected directly to the main vertical pipe in the same manner as those on upper floors, foul water would be forced back through the trap into the fitting. This can be avoided by taking all ground-floor wastes directly to the under- ground drain, independently of the main waste pipe, as shown in Fig. 301. ‘A typical installation for a six-storeyed block of flats, with bath, lavatory basin and W.C. on each floor, would be likely to have a 4-inch soil-pipe, 3-inch main ventilating stack, 2-inch anti-siphon- age branches from W.C., and 1}-inch wastes and vents from baths and basins. The saving in cost, in an example of this type and assuming first-class workmanship and materials, may be as much as 20 per cent. in favour of “one-pipe” plumbing. There would be little gain, however, when applying “‘one-pipe” plumbing to small suburban dwellings on two floors only. “Single-stack” Plumbing. For some time past, at time of writing, the Building Research Station has been carrying out laboratory experiments and the London County Council has been trying out practical tests (at Fulham and elsewhere) on a further development of “‘one-pipe” plumbing, resulting in a still greater reduction of cost. The savings, of course, vary with the par- ticular layout and the number of floors in the building being serviced, but the estimated relative costs of the plumbing for a five-storey block of flats, taking “standard” plumbing as 100 per cent., is as follows: 294 THE BUILDING—ITS SANITARY FITTINGS, ETC. Standard plumbing . . 100 per cent. One-pipe plumbing . . 80 ,, ,, Single-stack plumbing . 60 ,, ,, Briefly, the “single-stack” system proposes to increase the ‘‘general-purpose” soil-pipe by half an inch in diameter over and above what would otherwise be necessary—(e.g. 4-inch soil-pipe instead of 3}-inch for an average case), to concentrate the sanitary fittings (both soil and waste) as closely around the “single stack” as possible on the various floors, and to omit completely anti- siphonage pipes, allowing the small addition to the diameter of the general-purpose soil-pipe to act as conduit to the descending water and channel for fluctuating air stream required for anti- siphonage purposes. Observations through transparent plastic pipes in a full-scale model have shown that the water descending from W.C.’s, baths etc., is seldom sufficient to fill more than a small fraction of the pipe, and that the flow tends to descend along the inner walls of the pipe, while the air (shown by smoke in the model) tends to ascend by the centre of the pipe, which is free of water. The most unlikely combinations of W.C. flushing, bath, basin and sink emptying on the several floors, and all made to synchronise, failed to do more than cause a water-level movement of more than $ inch in the traps of fittings not being used or flushed, provided certain precautions in design were carried out. Those precautions were: 1. W.C, traps should have a minimum seal of 2 inches and an outlet not exceeding 34 inches. 2. W.C.’s and soil fittings should branch into the soil-pipe with a curved junction of 2 inches radius. 83. Waste fittings should be trapped with a minimum seal of 3 inches. 4. Basins should have a trap and waste pipe of 1} inch diameter and a maximum length of branch of 5 feet 6 inches. 5. Baths and sinks should have a trap and waste pipe 1} inch diameter and a maximum length of branch of 7 feet (owing to the slower rate of draining tending to refill trap even if siphoned). 6. Ground-floor fittings, to discharge into soil-pipe at least 3 feet above level of drain invert (to avoid backing up) or to be connected directly into drain at a level lower than the soil-pipe junction, 7. If “single-stack” to some fittings on more than five floors, a “relief” anti-siphonage pipe, 2 inches in diameter, to be fitted to a THE BUILDING—ITS SANITARY FITTINGS, ETC. 295 ground-floor W.C. outlet, and carried up, without branches to any other fittings, to rejoin the soil-pipe above the level of the highest branch, or to be allowed free vent at eaves level if more convenient. 8. The “single-stack” soil-pipe should join the drain at its base by means of an easy bend (radius about twice the diameter of the ipe). 9. Until further experiments have been carried out on tall build- ings, it is suggested that extra precautions should be taken to prevent siphonage of waste or soil branches serving fittings on the sixth and higher floors. It must be kept in mind that the single-stack system at date of writing (June 1956) is not permitted by any known by-laws in this country, but the L.C.C. is very satisfied with its experiments and appears likely to modify its by-laws to permit its use in the near future. If it does so, it is probable that the Model Code and local by-laws up and down the country will follow its example. It is a case where students should keep a watchful eye on the professional papers to watch for further developments, Having dealt with the waste matter down to ground level, the next chapter will deal with the underground drainage.