CHAPTER X THE BuILpING—ItTs DRAINAGE (Part 2)

10-50 = 35-25 feet at the lower end, and 27-41 + 10:50 = 87-91 feet at the other end. Suppose that when the level has been set up properly as shown, we find on sighting upon a bench mark, or other point whose level has previously been determined, that the height of the line of colli- mation of the telescope is 40-53. Then the sight rail at the lower end must be set up, quite level, so that a staff held on its upper edge reads 40:53 — 35-25 = 5-28 feet, while at the upper end of the drain the sight rail must be fixed so that a staff held on it reads 40-53 — 87-91 = 2-62 feet. The boning rod is then adjusted, by its clamping screws, so that its length is exactly 10-50 feet. Adjustment for Line and Gradient. For the purpose of laying the pipes to the exact line, the centre of the trench should be marked on each sight rail, and a plumb-bob suspended from this point by a fairly stout cord. Each pipe must be firmly bedded in the line joining these cords, its exact level being secured by the pipe layer inserting the shoe of the boning-rod upon the invert of the pipe and keeping the rod upright. The overlooker then applies his eye to the lower sight rail to see whether the top edge of the cross head of the boning-rod is above or below the line of sight from rail to rail. If it is above, the ground must be trimmed away and the pipe lowered until the true grade is reached. Should it be below, it should be gently raised and packed with concrete. The trench should not be cut wider than is necessary to allow sufficient room for the pipe layer to work at the bottom. The length opened up at one time must be governed by the number of _ THE BUILDING—ITS DRAINAGE 837 men at work, the nature of the ground and the interference with access to the premises. Where the ground is bad from wet sand or other causes, or in passing close to walls and buildings, where the foundations may be liable to disturbance by reason of the trench being kept open, it should only be cut in short lengths and with especial care. Timbering Trenches. As the excavation of the trench proceeds, the sides should, unless the soil is very firm and the depth of the drain small, be supported by proper timbering, fixed by competent timber men. A method applicable to ordinary cases of moderately firm earth is to place vertical boards about 9 inches by 14 inches in section, termed poling boards, at frequent intervals, or close together, according to the nature of the ground, supported by horizontal timbers about 9 inches by 3 in section, termed walings. The walings are kept apart by struts, about 4 inches square, wedged tightly between them. The struts should not be nearer together than about 6 feet, or they will interfere with the work of the pipe layer too much. In the method described the timbering cannot be placed in position until the ground has been excavated to the depth of the poling boards; if the ground is too loose for this to be done safely, it is necessary to increase the thickness of the boards to 2 inches and to point their feet, so that they may be gradually driven down as the excavation proceeds. Boards driven in this way are usually called “runners”. In a very deep trench, the method of timbering is best carried out on the lines shown in Fig. 362, in which two settings of runners are pointed at the foot and driven in. If the ground is very bad, the walings can be omitted, the trench being timbered by means of horizontal planks or sheet- ing, placed close together, secured by vertical polings about 9 inches by 3 in section, and about 6 feet apart, secured by strong struts as before described. Where the ground is very bad too, it may be advisable to leave the lower timbering in permanently. “Grips”’ or Handlocks for Making Drain Joints. If the bed of the trench is of good firm earth, and the local by-laws do not require a concrete bed to be used, the pipes can be firmly bedded throughout their length by forming grips or sinkings under each socket, as in Fig. 363. This gives a firm bed to the pipe, and enables the pipe layer to get his hand under the socket to make the joint, but the work has to be done entirely by “feel”, it being impossible to see the joint underneath the pipe. Concrete Under Pipes. When the ground is not very good, and in any case if the local by-laws require it, the pipes should be laid on a bed of concrete, at least equal to the diameter of the pipes ——— 838 THE BUILDING—ITS DRAINAGE 357 & 358 SHOW ONE FORM OF ™ RAMP TO REDUCE EXCESSIVE 359 VELOCITY IN DRAINS OF STEEP- SIGHT RAILS LY SLOPING S/TES AND BONING RODS 361 EXAMPLE TO SHOW USE OF SURVEYORS LEVEL TO SET UP SIGHT RAILS TO GIVE CORRECT GRADIENT THE BUILDING—ITS DRAINAGE 889 or of such thickness as the local by-laws direct. This is known as “bedding” the pipes. The by-laws may require “haunching”, in which case the concrete is added to and sloped off to form the section shown in Fig. 364. Under buildings; under drives or tracks likely to be traversed by heavy lorries; or where the drains must be less than 18 inches deep, the drain, if of stoneware, should be “surrounded” with concrete, as explained in Chapter LX. When concrete is to be used as either ‘‘ bedding”, “ haunching” or “surrounding”, it may be preferred to lay the first 3 inches of concrete in the bottom of the trench, and to lay the pipes on bricks, placed one behind each socket, with a pat of stiff mortar between the brick and the pipe. This gives ample room for making and inspecting the joints, and saves the time and trouble needed in cutting “grips” in the concrete under each joint. This method should be permitted only if the space under the pipes and between the bricks is now packed in with fine concrete so that the requisite depth of concrete foundation is completed and a complete support provided for the whole pipe-line. The bricks are subsequently completely concreted in and then left as a “bedding” or added to, to provide “haunching” or “surrounding” as the needs of the case or the local by-laws may require. Bad Ground. Where the ground is exceptionally bad and wet, mere concrete alone is sometimes not sufficient support. The usual method of procedure in such a case is to drive in timber piles at intervals along the sides of the trench, connect them by pieces of timber spanning the trench, and lay a foundation of elm planks from one to the other to carry the concrete. An alternative method would be to reinforce the concrete, by embedding in it steel-mesh reinforcement. If the nature of the sewage permits the use of iron pipes, they provide the best way out of the difficulty. Timber piles, about 6 inches square, can be driven in at a distance apart equal to the outside diameter of the pipe and the pipe can be supported on cross pieces, as shown In Fig. 365. Use of Badger. We may now revert to the case of the.stoneware drain laid under ordinary conditions. As each pipe is jointed, a “badger” should be drawn through, in order to remove any mortar which may have found its way through the joint. In its ordinary form, a badger consists of a semi-circular piece of wood having, preferably, a rubber ring projecting from its curved edge. A handle about 3 feet long completes its construction, An im- proved form of this appliance is shown in Fig. 866 consisting of two circular discs of wood, edged with rubber bands and connected 340 THE BUILDING—ITS DRAINAGE by a steel spiral spring, which enables the badger to be drawn through a bend. Testing New Drains. The drain having been laid and jointed, it should next be inspected and tested by the surveyor. He should walk along the trench, inspecting both pipes and joints, marking any defects with chalk as he goes. After the work has been completed not less than twenty-four hours, he should apply the water test, in order to determine the water-tightness of the drain. The method of doing this will be fully dealt with under the heading of sanitary surveys. Filling in Trenches. If found all in order the trench can be filled in. This is a matter requiring careful supervision, as damage is easily done by falling stones or brickbats. For the first foot of depth over the pipes, the earth should be freed from stones; after depositing it in the trench it should be well but carefully rammed or consolidated. The filling in should be completed in layers of not more than 1 foot in depth, each layer being well rammed. On completion, the drain should be again tested in order to detect any damage during the filling in. It is a good plan to make the con- tractor responsible for the drain standing the water test three months after completion, in order to ensure the use of cement in proper condition and of good quality. Connection to Sewer. The connection to the sewer is a matter calling for mention. In developing an estate, junctions are often put in the sewer opposite the various plots. The mouth of the branch of the junction is sometimes closed by means of a piece of slate, but this is a slipshod and unsatisfactory practice. Proper junctions, sometimes called “joinders”, can be obtained for the purpose, having the branch temporarily but securely closed, as shown in Fig. 867. In this example a cap is formed as part of the junction, a fairly deep triangular groove being formed round it. A few taps with a cold chisel readily detaches it, leaving the socket free for the connection of the drain. If a junction has not been put in, it is a frequent practice to remove two or three pipes in order to build one in. This can be obviated by the use of the special junction shown in Figs. 868-369. One pipe only need be removed. From the plan given in F ig. 368 it will be seen that the junction has a very long socket, but, as shown in side elevation, Fig. 869, this socket is only applied to the lower half of the pipe. After the junction has been jointed to the two pipes A and B, the open space at S, due to the presence of only a half-socket, is closed by a short piece of pipe having a double socket on its upper half only, as shown in section in Fig. 870. THE BUILDING—ITS DRAINAGE wa ES S SNA KX YN SSH Mar NOT) 39863 GRIPS OR HOLLOWS /N BOTTOM OF TRENCH OR CONCRETE, 70 PROV- /DE ROOM FOR MAK/NG THE JO/N7TS 364 F CONCRETE FOUNDATION * HAUNCHED UP 70 TOP OF % DRAIN 62 ‘ TIMBERING FOR DEEP TRENCHES 341 TIMBER “SUPPORTS LEFT IN, WHEN FILLING /N / 7T GR , se uiuadletteat, nanan WHEN GROUND /S BAD SEALED SOCKET OR OINDER? FOR JUNCTION OF BRANCH /JMPROVED FORM DRAINS WITH SERVICE SEWER OF BADGER AT LATER DATE 368-370 SHOW A SPECIAL JUNCTION P/PE TO CONNECT DRAIN TO SEWER WHEN NO PROVISION HAS BEEN MADE 842 THE BUILDING—ITS DRAINAGE Cesspools. In the case of country districts there may be no sewer, and the house may not be of sufficient size to justify the installation of a sewage-disposal installation of its own. Recourse must then be had to a cesspool. The usual official requirements as to cesspools are: It shall (1) be not less than 50 feet from a dwelling; (2) be not less than 60 feet from any well, spring, or other source of water supply; (3) be readily accessible for cleansing, and in such a position as will obviate the contents being carried through a building; (4) have no connection with a sewer or watercourse; (5) be disconnected from the drain by means of an intercepting trap; (6) be of brick- work built in cement mortar on a bed of concrete, cement rendered or asphalted inside, and backed with not less than 9 inches of clay puddle if the soil is waterlogged; (7) be covered, ventilated, and have means of access. Cesspools may be either rectangular or circular on plan and a very usual rule for size is to allow 1 cubic foot per day for say 100 days for each person expected to be in occupation. This is not a generous allowance, and it is assumed that bath and basin water will be led to a soak-away and that all rainwater will be excluded. Fig. 371 shows a section through a good type of cesspool for houses in remote districts where there is no public cesspool emptying service. It is of circular plan and domed over, built of brickwork, cement rendered, and backed by clay puddle; the floor is of con- crete, falling to a sump or sinking in the middle, and with a foot of clay puddle below it as an alternative to concrete. It has an access shaft covered by a stone slab or manhole cover at M.H.C. It is ventilated by forming a breathing chamber having a grating over it at B.H.C. This is about 18 inches square on plan, and is constructed as follows: A short length of 9-inch pipe is built into the dome to form a breathing hole, B.H. Over this is placed a galvanised iron grating. The chamber is then filled with broken stone, such as road metal, and completed by a grating. The inlet is at I. In some eases it is desired to utilise the sewage for the kitchen garden, and this is best accomplished by the provision of a chain pump, such as shown in the figure at P. The essential part consists of the pump tube and an endless chain carrying circular iron dises at intervals of about 9 inches. These dises carry the sewage up the pipe when the handle is turned and dis- charge it from the mouth of the pump. The figure shows a plan of the ground above the cesspool, and gives the relative positions of the parts. It will be seen that an intercepting chamber is provided close to the cesspool. If some distance from any THE BUILDING—ITS DRAINAGE 343 PW 7, WEE 371, PLAN AND SECTION OF CIRCULAR CESSPOOL, WITH CHAIN PUMP, SUITABLE FOR REMOTE DISTRICT WHERE NO PUBLIC EMPTYING SYSTEM EX/STS AND HOUSEHOLDER HAS TO DISPOSE OF CONTENTS BY SPREADING QVER OWN OR NE/GHBOURING FARM LAND ANO PLOUGHING IN, SS AG Z ‘ GO YX GY zs 372. PLAN AND SECTION OF RECTANGULAR CESSPOOL, WITH SUMP AND MANHOLE COVER, SUITABLE FOR DISTRICT WHERE LOCAL AUTHORITY EMPTIES AT REGULAR INTERVALS BY CESS~ POOL EMPTYING TANKER WITH MOTOR PUMP ANO ARMOURED HOSE, 344 THE BUILDING—ITS DRAINAGE building, the cover of the intercepting chamber can be in the form of a grating, to act as a fresh-air inlet to the drains. If the local authority undertakes to empty the cesspool at regular intervals by means of a motor tanker provided with a suction pump and several lengths of armoured hose, the chain pump illustrated can be omitted, and the form shown in Fig. 872 may be found preferable. Sewage Lifts. It is sometimes necessary to adopt means for lifting sewage from a drain to a sewer, as where a building has a deep basement. Pumps of small capacity, even though of the centrifugal type, are liable to become choked by the solid matter in the sewage, and lifting by means of compressed air will usually be preferable. The two types of apparatus most used are the Sewage Lift and the Ejector. The former will be preferred on small schemes where there is an ample water supply at good pressure, the latter where there is electric power available. The arrangement of the parts of the Sewage Lift is shown dia- grammatically in Fig. 873. It is worked by means of an automatic flushing tank and the principle is very simple. The flushing tank is placed fairly high up in the building, and the other chambers in approximately the positions shown. The drains discharge into a sewage-collecting chamber, from which the sewage flows to the forcing chamber, being prevented from returning by a non-return valve. When the sewage reaches a certain level in the collecting chamber, it opens the reverse action ball valve, R.A.B.V., and allows the automatic flushing tank to fill. The latter in due course discharges, expelling and compressing the air in the air chamber, which exerts a pressure on the sewage in the foreing chamber and drives it up through the forcing main to the high level drain, D. The capacity of the automatic flushing tank is greater than that of the air chamber; sufficiently so to enable the water not only to fill the latter, but also to charge the siphon and so empty the water, after it has done its work, into the used water tank, from which it can be utilised for any other than domestic purposes, such, for example, as drain flushing. After the air chamber has been emptied of water in this way, it is re- charged with air from the vent pipe connected to the flush pipe, which is now empty. The sewage-collecting chamber is provided with a fresh-air inlet pipe, communicating with the outside air. An inspection chamber is provided just outside the building, with an access cap, A.C. The Shone Sewage Ejector. The Shone ejector is similar only in the