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inserting a junction, &c. The above remarks apply to house branches as well as to main sewers, and it is very important not to omit the insertion of inspection pipes, of some kind or another, at proper intervals and suitable places, in house sewers, especially those of large mansions.
The main sewers should be freely ventilated at the level of the streets. All attempts to ventilate them in any other manner have been, without any exception, signal failures. If the ventilators, whether of main or of branch sewers, cause a nuisance, it is because there are not enough of them, or because the sewer is either badly laid or not properly flushed. In country places especially, cesspools are often the destination of the house sewers. Cesspools should never be made where it can be helped. It is far better to use the sewage on the land than to collect it in cesspools. However, in some places, cesspools are necessary, in which case they should always be made impervious to water, by being built of bricks set in cement and rendered in cement. The cesspool should not be under the house, but at some distance, and it must be ventilated. If near to the house, the ventilator should be carried up outside the wall of the house, and above the ridge of the roof. If at some distance, it may be ventilated either by means of an open galvanized iron grating, or by means of iron pipes carried up a tree and covered with wire network at the top. The cesspool should not overflow into a stream, or drain running into a stream, but on to the surface of the ground; and it is folly to build a second cesspool, as some people do, for the first one to overflow into, for, by the same argument, one might build any number -one after the other. Brick sewers should never be used under houses. The foul water soaks through them into the soil, and sediment is liable to accumulate in them. Rats eat their way through them, displacing the bricks and wandering about the house, and so not only does foul water get out of them into the soil, but foul air finds its way wherever the rats go, besides the fact that rats carry filth from the sewer itself about the house, and into the larder if they can get there. In this way, I have no doubt whatever, that milk and other foods have disease poisons frequently conveyed to them. Sewers made of glazed stoneware pipes should always be used for houses, except in cases where it may be better to use iron pipes, and they should always be laid outside the walls of the houses whenever it is practicable. They may require to be laid in a bed of concrete, as for example, where there is much made ground, or to be laid on hollow invert blocks in very wet soils. They should be jointed with cement, or, where a settlement is feared, with clay, finishing with a ring of cement. Clay alone is not advisable, as it is apt to get washed out of the joint, in which case the water runs out into the soil, and the solid matters accumulate in the sewer. If pipes, with Stanford's patent joint, made by Messrs. Doulton & Co. (of which I have some examples here) are used, no cement is required. The ends merely have to be greased and fitted into one another. These pipes must be laid straight, or they will not fit together, and at bends it is often requisite to use ordinary socketed pipes. The fall of a house sewer should at least be 1 in 48, but a more considerable fall is preferable; 9-inch pipes may be used for very large mansions, especially if outbuildings are connected with the sewer, but, as a rule, for private houses 6-inch pipes with 4-inch branches are amply large. The junction of the branches should never be made at right angles, but always at an acute angle, and of course in the direction in which the water is going. At the end of the house sewer, in the main sewer, or cesspool, a swinging flap made with galvanized iron is frequently placed, with the view of keeping rats out of the house sewers. It may be of some use for this purpose, but is of little use for preventing the entrance of foul air, and as may be expected, these flaps are often out of order. It is also usual to place a watertrap of some kind upon the house sewer before it enters the main or cesspool. The kind formerly most used was what is known as the dipstone trap. The drain was deepened at the spot, and a piece of stone or slate inserted right across the drain from side to side, and reaching from the top down into the deepened part, two or three inches below the level of the bottom of the sewer. Water of course always remained in the deepened part, and so the dipstone running right across the drain dipped about two or three inches into this water. As it reached also to the top, and was built in, it obviously prevented the passage of the sewer air from the main sewer or cesspool into the house sewer, except, at any rate, that which could pass through the water in the trap. These traps were usually made rectangular, and were often very large, so that they were practically cess