Whether a brick drain or a pipe drain, it should be trapped before it is connected with the main sewer or cesspool. This trap, in the case of a brick drain called a “dipstone” trap, is a brick pit with a stone across it from one side to another, and dipped into the water which remains in the pit. The object of this stone is to prevent foul air coming into the house. As a matter of fact, the pit holds a large collection of foul matter and becomes a small cesspool, indeed, there is no difference between them. A drain may be made of glazed stoneware pipes, which may be joined together in one of several ways. They may be laid “dry,” i.e. without any jointing material between the ends, in which case they are, of course, not water-tight; or they may have clay in the joints, in which case you cannot fill them with water--that is to say, they will not hold water under pressure. (If you fill them with water, by plugging at the lower end, the water will come out at the joints.) Or they may be laid with the pipes the wrong way. When the joints are made with clay they will very soon become leaky; and when that happens, the water oozes through the joints, filth collects in the trap, and it gradually plugs up the whole drain from one end to the other. This may go on for years without being found out, and so cause the ground under the house to gradually become a large cesspool. This is an extreme case. Or they may be jointed with cement, and there are some other ways. They may be perfectly well jointed with cement, so as to be water-tight. The drains, then, should answer to this test, i.e. you should be able to plug them at the lower end, and fill them with water. They should not be under the house, if possible. In London we cannot help it as a rule. If under the house, the straighter the course of the drain the better. Do not let it wind about in order to get away from different rooms. The best thing is to have a straight course through and to see that it is water-tight. It should hold water like a teacup. The drain must not be directly connected with the main sewer or merely separated by a siphon trap; but there should be an air inlet into the drain between the siphon trap and the house. This opening may be of different kinds. The best kind is that of a manhole for access to the drain and trap (so that the trap can be examined and cleared out at any time); the air inlet should be a grating either over the manhole or in the nearest wall opening into a pipe leading into the manhole.