As a matter of fact, total obstruction or stoppage has been discovered in 6 per cent. of the houses which have been inspected.
The next point worthy of attention is the soil pipe; this term being at present used to signify the vertical portion of the drain only, although it very often is also used as meaning the almost horizontal drain under the house.
The soil pipe is of lead. This is an excellent material if the pipe be properly arranged, but here it is not. The great fault is that there is no ventilation. As a consequence, the upper part of the pipe will always be filled with sewer gas, which tends to rise in a somewhat concentrated state. Now, sewer gas has a powerful action on lead, and, therefore, a soil pipe arranged without ventilation never stands many years before it becomes “holed,” that is to say, is worn through at its upper part. When this occurs, of course, there is ventilation enough, but it is into the house. The ventilation in this case will, in fact, be most active, because every house, on account of the fires in it, acts, especially in winter, as a chimney, and draws in sewer or other gas from every possible crevice.
At the top of the soil pipe will be found the commonest of all water-closet arrangements, namely, the pan-closet with D trap. This arrangement is exceedingly well known: it is a most skilfully devised piece of apparatus for retaining sewage in the house, and distilling sewer gas from the same, and it is the cause of probably nine out of ten of the actual smells perceived in houses, even if it does not (as some say) give rise to much actual disease.
The soil pipe discharges over a small cesspool at the foot. This is a very common arrangement. The cesspool is usually dignified by the name of a dip trap. The percentage of houses showing leaky soil pipes is 31.
Now, observe that, although our constructor has not ventilated his soil pipe, he has been careful not to leave the system entirely without ventilation. On the contrary, by the simple device of leaving a rain-water pipe untrapped at the foot, he has ventilated the drains, and also the public sewer, into the back bedroom windows! This is a quite common arrangement, and frequently results in typhoid fever.
Next, in order, we may take the case of the discharge pipes from baths, sinks, basins, and all such appliances. It has been laid down as a rule by the best sanitary authorities that these appliances must discharge not into the soil drains, but into the open air over trapped gullies, as it has been found that this is the only way of being absolutely certain that no sewer air shall enter the rooms by the discharge pipes. It is quite true that if a trap be fixed on a discharge pipe of, say, a sink, the greater part of the sewer air may be kept back from the house; but traps, however excellent they may be in assisting to keep out sewer air, are not alone sufficient. There are several reasons for this. In the first place, there is the fact that a certain amount of sewer gas will pass through the water of a trap, or, to speak more strictly, will be absorbed by the water on one side, and afterwards given off on the other side. It is true that in the case of a well-ventilated drain this amount will be infinitesimal, and might even be disregarded, but there are other causes for the uncertainty of a trap. If the appliance, on the discharge pipe of which it is, be disused for a long time, there is the possibility that the water in the trap may dry. In this case, of course, there is no further security. Besides this, however, there is an action known as siphonage, in which the rush of water through a pipe carries with it the water which ought to remain in the trap and form a seal. In Fig. 21 are shown several different ways of connecting sinks, &c., with drains. The discharge pipe often carries an apology for a trap, in the form of a little apparatus called a bell trap. But, as a matter of fact, it is the commonest thing possible to find the bell trap lying on the sink. It has been lifted out of its place to let the water run down the waste pipe more quickly. It is no unusual thing to go into the scullery of a house, and to find the discharge pipe of the sink quite open, and a blast of sewer air issuing from it which will extinguish a candle.
In other cases the sink has an arrangement which is called a grease trap, but is, in reality, nothing more nor less than a particularly foul cesspool. It calls for little remark. The pipe from the sink dips into the foul water to make a trap. In many cases, the pipe does not dip into the water; but there is a bell at the top. Sometimes the drain is at various places made up with bricks. This is a very common thing to find in houses. The bricks are used to save the trouble of getting special junction bends, &c. The other sinks and baths in the house are shown as discharging into the closet traps. This is a very common and objectionable arrangement. Sixty-eight per cent. of houses examined show the defects last mentioned; that is to say, the sinks, baths, or fixed basins are connected with the drain or soil pipe, a trap of some kind generally, but not always, forming a partial security against sewer gas.
As mentioned before, the only ventilation in this case is such as will permit the issuing sewer gas to find its way into the house. It is by no means unusual to find no provision at all for ventilation, or to find the ventilating pipes so small that they are totally useless. In more cases than one, Burton found the soil pipe carried up as a rain-water pipe into the attics, where it received rain-water from two gutters, one from each side of the roof, and discharged all the sewer gas which escaped by it. Generally, the drinking-water cisterns are situated in such attics.
It may be noted, in the other drawing (Fig. 21), that a trap is fixed on the main drain, which will keep back almost all sewer gas, and that ventilating pipes are so arranged that a constant circulation of fresh air exists through the whole drainage system, and will carry away with it any little sewer gas which passes through the trapping water.