Sewer Construction and Quality Issues

When sewers are laid to a town or district, it is the practice of the authorities to let the work by tender, the lowest tender being oftentimes accepted ; consequently it is in the interest of the contractor to get the work done as quickly and cheaply as possible. It is impossible for the engineer, or clerk of works, to see the whole of the work done, and the result is that a large quantity of bricks which form the sewer are not properly bedded. Liquid sewage finds its way through the joints of the brickwork and percolates through the soil, in some cases to a very con- 10 BAD DRAINS; siderable distance, contaminating the water it mixes with on its course, and oftentimes it forms a putrid mass under the basement of buildings which happen to be of a lower level than the sewers, To prevent this, a clause should be inserted in the contract that each length of drain or sewer should be tested by atmospheric pressure, say 5 Ib. to a square inch. The top of the sewer should be as tight as the bottom to prevent any gas escaping through the sandy soil or rubble which may be filled in around the sewers or drains. Leaky sewers and badly-jointed pipes under the soil should never be allowed, yet the danger is not so great in them as in those pipes laid above the ground. Joints to these pipes so often leak that without testing them thoroughly when laid, one leaky joint would cause an unpleasant odour in a building for years without its source being dis- covered. The reason of this is, that the current of air passes through buildings in a thousand different ways. I have known a sickly odour to come from a cupboard on the first floor of the wing of a building some 60 feet from any soil-pipe or grating ; one case in particular, that of a nursery cupboard. This occurred through a leaky soil-pipe from the closet in the basement of the building. From the planning of the building the chimney near the cupboard had the greatest draught of air AND HOW TO TEST THEM. 11 in the house, and the air which supplied this chimney came principally from the basement. The sewer gas from the leaky joint, being of a heavier gravity than the atmosphere of the house, was carried along the floor unobserved to this particular room, filling at night, when the fire was not burning, this cupboard, which contained linen, and this held the impurities given off from the leaky joint in the pipe. Many cases of a similar nature could be men- tioned, where families will never recover the loss sustained by them through similar leaky joints in the soil-pipes. Insufficient fall to sewers does not often occur in those laid under the supervision of engineers, but it is in the branch drains connected to them where so many blunders are made. Oftentimes one part of a drain is laid almost level, whilst another part is laid with a steep gradient. This facilitates the choking of drains, and the siphoning of traps. Some persons lay drains from houses to the main sewer or to branch drains which are altogether out of proportion to the work they have to do. The smaller the drain is kept the better, but the diameter should be regulated according to the quantity of water and soil flowing into it, taking into consideration the possibility of additional inlets being added. 12 BAD DRAINS; The best plan is to collect the number of inlets or supplies to the drain, compare them with the gradient to which they are laid, and put in a drain which, if all the inlets are supplying water at the same time, would not fill more than nine-tenths of its area, In some cases I have seen a 9-inch drain laid from a house having only two closets, sink and bath outlet attached. If the whole of these were used at the same time, the area of the flow into the drain would only be 7696 inches, but in the 9-inch drain the area would be 63°617 inches, or nearly nine times the size required to carry off the water and soil. The whole space not occupied by water and soil is filled with gas, which extracts poisons from sewage and distributes them at outlets according to the displacement caused by the water and soil entering and flowing through the drain. Architects and builders laying drains to houses or buildings should discard the theories of any persons who do not keep to this rule: that the smaller the drain is, the better, providing it does not fill ; and the least quantity of gas there is in the drain, the less dangerous will be the poison in the gas when dis- charged through openings or gratings. The reason of this is, that in a small drain only a small quantity of the sewage is exposed to the action of AND HOW TO TEST THEM. 18 the gas in transit; whereas in a large drain the greater portion of the sewage is exposed, thus in- creasing its decomposition. When storm water from houses or land enters drains, great care should be taken to form openings or inlets near where drains are likely to fill, as the injurious effects of trap siphoning are of serious consequence to health. In many cases the construction of new drains and sewers in a district have been simply a waste of money as regards improving the health of the inhabitants, and numerous cases of zymotic disease, and in some cases an epidemic has occurred where previously such diseases were almost unknown. This is caused principally by connecting old drains (some of which are disused ones and connected with old cesspits) to the new drains leading to the sewers, In cesspits and old drains the soil and putrid matter have been for years allowed to accumulate, and the poison from such matter, when distributed into the open air through gratings in the new sewers or into houses, is, when inhaled into the system, the cause of these zymotic outbreaks. In tracing these old drains and in preventing stagnant gases from remaining in any portion of the drain, the engineer or architect cannot pay too much attention, as confined gases when charged with poisons from 14 BAD DRAINS ; putrid matter are the principal factors in producing disease. Many persons place a well-constructed trap at the inlet, and another some distance along the drain, say at the end of a building or grounds, without any ventilation between the two traps. In fact this used to be a common occurrence; but it should never be done. If the drain should be a 6-inch one, and the traps 50 feet apart, the amount of gas between the two traps would average 9 cubic feet, and this gas would in the ordinary working of the drain remain for years, getting more poisonous the longer it remained undisturbed. The owner of the house, knowing that he had a good trapped drain connected to sewers, would feel himself safe, and naturally think his house healthy. Far better for him if the house were drained into a ventilated cess- pit, as when the gases in the drain became released, which may occur by the siphoning of the traps at the house-connection, the danger would be equal to the emptying of a disused cesspit, and carrying the contents through the house. The more a person tests the working of gas in sewers or drains the more he will find that branch drains from their construction supply the poisons which render the gases in the sewers themselves so noxious. In 1880, whilst engaged in tracing the course of an outbreak of typhoid, I made a series of experi- AND HOW TO TEST THEM. 15 ments with a view to trace the source from which the disease emanated, and every experiment proved that the origin of the disease lay in the gases which were in contact with putrid sewage matter, existing in old drains and cesspits attached to the sewers as well as in the gases which were confined between traps. The distribution of the disease was due to the imperfect construction of the sewers, drains, and sanitary fittings. The most successful experiment, and the one from which the greatest result was obtained, and which I have ever since most successfully used, was in deter- mining the state, size, and condition of the drains un- derground, and also that of the house or buildings, by measuring by compression the gas contained in the sewer or sanitary fittings. The principal cause of its distribution was the compression of the gas between the water-traps, the siphoning of house-traps leay- ing at times a free passage for the gas to enter the house. The amount of compression or displacement necessary to force the gas in bulk through the traps has been accurately measured, to know what quan- tity of liquid was required to be thrown into a drain or sewer of any size to force the gas in bulk through the water-trap. The lifting power of the gas on the water by compression was found to be séo part of its bulk. Thus, if a drain perfectly 16 BAD DRAINS; sound, and sealed with a water-seal each end, held 300 feet of gas, 1 cubic foot of water thrown into the drain would force the gas in bulk through the water-seal, . It became evident that if both ends of any drain were sealed with a water-trap or otherwise for test- ing, the capacity of the drain or leaks of any kind could be determined without excavating, As it was inconvenient to watch the working of the drain through the traps, I constructed an instru- ment called a detector * to observe the working of the atmosphere in the drain. This instrument, or a gas-pressure gauge, when attached to the drain, will denote by the rising of the liquid the amount of compression in thedrain. This, when compared with the quantity of water thrown into it, will give the size and capacity of the drain, and will also indicate any siphoning of traps or leaks which exist in any of the sanitary fittings of the house. The following table will show the amount of gas in every 100 feet of circular pipe or drain, from 4 to 30 inches in diameter, also the amount of water thrown into a trap to produce the necessary pressure of gas to lift the liquid 1 inch in the * This instrament with instructions as to reagents can be obtained from E. Cetti, Meteorological Instrument Maker, 36, Brooke Street, Holborn, price 12¢, 8d. It is cheaper and more convenient than the pressure-gauge, and registers any pressure during the testing of drains, r Plate 1. AND HOW TO TEST THEM. 17 detector or pressure gauge: the quantity being as near as possible 3} ozs. of water to 1 cubic foot of gas space. Peal Gan in each 100 foot. ‘eprdnes toes ‘Area of Pipe Ty Draln?®|lebeth of Drato Pipe | rine of Liguid in | 1728 = 1 cuble fot t sia OTT 12°566 6 193988 040 28-274 9 443M, 112 63-617 12 TBA 205 118-097 15 1224443 316 176-715 18 176443 450 254-469 19 1964449 511 283-529 20 218.8%, 557 814-160 21 240,85 621 346-361 22 2683985 670 380-138 23 288 8k 742 415-476 py SILAS, 816 452-390 25 3401 870 490-875 26 3683943 9 418 530-930 27 3974993 10 214 572556 28 4QTHSE ui2 615758 29 4581994 u7s8 660° 521 30 49044 12.6 9 706-860 The method of testing drains and fittings by com- pression of gas is as follows:—When the drainage c 18 BAD DRAINS; plan of a building exists, the work of testing by compression of gas in the drain will be a very simple matter. Plate 1 shows the drains as laid to a semi- detached villa, with two inlets from sinks marked I, one from bath overflow marked 2, and two from the soil-pipes of closets in the basement and first- floor marked 3. The drain from A to B is a 6-inch stoneware pipe, and its length is 100 feet. The amount of gas in it would be 19399 cubic feet. The branch drains from the other inlets are 4 inches in diameter, and the collected lengths are 50 feet, and the quantity of gas in them would be 445 cubic feet, giving a total in the whole of the drain of nearly 24 cubic feet. If the indiarubber pipe to the detector or pressure gauge is placed in either of the traps marked I, and the glass tube filled with liquid up to the data line, 5 pints of water poured into either of the traps marked I, will produce a rise of 1 inch in the liquid of the detector, that is if all the drains are clear and joints tight, the drains being stopped off for testing at A. Should a trap be fixed anywhere between A and B a lesser quantity will be required to lift the liquid, and the position of the trap can be determined by comparing the exact quantity of water used with the capacity or quantity of gas in the drain. AND HOW TO TEST THEM. 19 Ifa trap should be fixed or a stoppage formed in any part of the drain AB, the flushing of a closet or sink would, by the compression of the gas, force it in bulk through the weakest trap, or the one having the least dip or seal. The quantity which would pass through would depend on the amount of water used in the flushing and the fall of the drain. The drains to the building having been tested, and their defects ascertained, it will be necessary now to test the soil-pipe. On this plan it is fixed on the outside of the house, having a trap with an open grating just beyond the basement closet, and a ventilating pipe carried above the eaves of the roof. Whether the soil-pipe be fixed inside or outside of the building it should be perfectly gas-tight, and in this testing a person cannot be too particular. In testing the soil-pipe shown on plan, the easiest method is to put the detector or pressure-gauge at the grating of the trap 3, placing the indiarubber tube over the grating, and making a tight joint with clay. Then close the top of the ventilating pipe and pour water in the top closet, when, if the joints are tight, the liquid in the detector will rise suddenly, and then lower itself as the water leaves the trap, indicating that the soil-pipe is tight, but if it is not tight, no rising of the liquid will take place. Should there be no trap at the bottom c2