CHAPTER X THE BuILpING—ItTs DRAINAGE (Part 3)

sense that it is operated by compressed air. The compressed THR BUILDING—ITS DRAINAGE 345 VENT PIPE FLUSH PIPE S/PHON Wy Q ig Q « ¥S a Q wy YH re) wy oe Q 3 S WATER SUPPLY PIPE FORCING MA/N SEWAGE COLLECT/NG CHAMBER Ve SEWAGE LIFT OPERATED BY MAIN WATER SUPPLY, FOR USE IN BUILDING TOO LOW 70 DISCHARGE /N TO SEWER BY GRAVITY 846 THE BUILDING—ITS DRAINAGE air is, however, derived from an air-compressing plant. The system is applicable not only to the drainage of deep _base- ments, but also to the sewerage of low-lying districts. The ejector can be adopted for the raising of water, sewage or sewage sludge, and is usually installed in a brick chamber. The apparatus can be made of any size or shape convenient for the special conditions for which it is required. The air compressor will usually be driven by an electric motor, which arrangement enables the rate of working to be automatically regulated. In exceptional cases, where electric power is not available, an oil engine may be used. The Working of the Ejector. A diagrammatic section of an ejector is given in Fig. 874. The action of the apparatus is as follows: The sewage gravitates through the inlet pipe into the ejector and gradually rises therein until it reaches the underside of the bell B. The air at atmospheric pressure inside this bell is then enclosed and the sewage, continuing to rise outside and above the rim of the bell, compresses the enclosed air sufficiently to lift the bell, spindle, ete., which opens the compressed air admission valve, C.A.V. The compressed air, thus automatically admitted into the ejector, presses on the surface of the sewage, driving the whole of the contents before it, through the bell-mouthed opening at the bottom, and through the outlet pipe, to the high-level gravitating drain. The sewage can only escape from the ejector by the outlet pipe, as the instant the air pressure is admitted on to the surface of the liquid, the valve on the inlet pipe falls on its seat and pre- vents escape in that direction. The sewage passes out of the ejec- tor until its level therein reaches the cup, C, and still continuing to fall, leaves the cup full, until the weight of the liquid in the portion of the cup thus exposed, and unsupported by the surrounding liquid, is sufficient to pull down the bell and spindle, thereby re- versing the compressed air admission valve, which first cuts off the compressed air and then allows the air within the ejector to exhaust down to atmospheric pressure. The outlet valve then falls on its seat, retaining the liquid in the outlet pipe, and the sewage flows into the ejector once more, driving the free air before it through an air valve as the sewage rises; and so the action goes on as long as there is sewage to flow. The positions of the cup and bell floats are so adjusted that the compressed air is not admitted to the ejector until it is full of sewage, and the air is not allowed to exhaust until the ejector is emptied down to the discharge level. This method of draining basements has been very extensively adopted in the United States. THE BUILDING—ITS DRAINAGE 3847 particularly in Chicago, where the basements are, in many cases, of very considerable depth. Stable Drainage. The general practice in draining stables is now very different from what it used to be, it being recognised that openings to a drain, inside a stable building, are as likely to be injurious to horses as they are to human beings in a domestic building. The floor should be of hard, non-absorbent material, such as Staffordshire blue bricks, adamantine clinkers, or grano- lithic concrete. The stable should be drained by laying the paving so that the floor falls to shallow surface channels, connected to a main channel leading to a gully outside the building. In a large stable, the main channel should be of iron, and covered with a grating, as shown in section in Fig. 375. The chan- nel and grating should, of course, be protected against corrosion. The form of gully used for stable work should be different from that of the ordinary yard gully. It should have a perforated iron bucket to intercept particles of straw, horse dung, etc. The bucket is readily removable, like the tray of a grease trap. Such a gully is shown in section in Fig. 876. It would have the usual iron grating over. In other respects the drainage of a stable follows the general principles already given for domestic work. Petrol Interceptors. In the case of a garage a difficulty occurs that has not occurred in the cases already dealt with; that of the danger of petrol washings finding their way into the drainage system and possibly leading to explosions. By the Public Health Act, 1936, it is illegal to discharge into a sewer any petrol, or any other oil which gives off an inflammable vapour at a temperature of less than 78°F. In a small garage, attached to a building having a fair amount of land, the best thing to do is to lead the surface drainage of the garage to a soak-away pit, dug well away from the building, but in the case of a garage in a crowded district this is difficult if not impossible. The requirements of the London County Council may be given as an example of what should be done in other cases. Figs. 3877 and 878 show a section and plan of a special form of interceptor which they will accept as meeting the case, the example given being suitable for a garage taking six cars. It will be seen to consist of three chambers, each 3 feet square and 4} feet deep, built of brickwork on a concrete floor. Calling the chambers Nos. 1, 2 and 3, the only exit from No. 1 to No. 2 is through a pipe submerged to 12 inches from the floor, the pipe thus being far enough from the floor to avoid sludge passing. The only exit from No. 2 to No. 3 is by a pipe submerged 348 THE BUILDING—ITS DRAINAGE to 6 inches from the floor, while a similar pipe forms the outlet from chamber No. 8 to the drain. By this arrangement the petrol is left to accumulate at the top of the sewage in each chamber, any vapour being carried off by the ventilating pipes shown by dotted lines. Probably other means could be devised to get over this difficulty, but the example given shows what is at present required for London garages. Drain Repairs. In concluding this section a few words may be added on the repair of drains and on the remodelling of old drainage systems. In the ordinary way, on finding that a drain is leaky, one opens up the ground in order to expose the drain and so trace the leaky joints or cracked pipes. This necessitates the ground remaining open for at least a day or two, and often means taking up floors and so on. A system of repair has been in use for many years by a London company, based on the following lines: The drain is first cleaned out and disinfected, the disinfectant being applied under pressure, so that it will pass through any defects and so disinfect the sur- rounding soil. An appliance is then passed through the drain, charged with Portland cement grout, which, by means of com- pression, is forced into every flaw in either pipes or joints. The inside of the drain is said to be left free from any roughness due to this process, and the company is said to guarantee the drains to stand the water test on completion. The system has much to commend it where a drain is only slightly leaky, and the covering of the ground is a matter of great inconvenience, but it would be an inadequate means of dealing with a very bad case. Remodelling Old. Drains. The remodelling of old drainage systems is not a matter calling for a very extended notice. The principles which a new system should satisfy have been fully laid down in the preceding chapter, but it should be pointed out also that where, in remodelling a system, an old drain is discarded, the drain should be taken up and the trench disinfected before return- ing the earth. The extent to which an existing system is re- modelled is a matter dependent entirely on the circumstances of each individual case. In some cases, sound but moderate pro- posals would be certain to be carried out, and sanitary progress thereby furthered, while an elaborate proposal might lead to nothing much being done, and progress thereby retarded. Drain Rods and Fittings. For the cleansing of drains and the removal of stoppages, various tools are used, fixed to drain rods. The latter are of red malacea cane or of spiral and flexible steel spring, the usual length of each section being 8 feet with a total THE BUILDING—ITS DRAINAGE 349 length in the complete set or bundle of anything from 30 to 90 or 100 feet. The rods are fitted with screws and sockets, so that they may be put together to form a long rod. Various tools are used for fixing to the end of the rod, including fixed and hinged badgers, double *corkserews’’, spring hooks, ete., for the purpose of remov- ing obstructions. After the removal, the drain can be finally swept out by a circu- lar brush of either bass or whalebone, affixed to the end of the rods.