This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
The last paragraph of By-law 62 provides that every inlet to a drain, not being an inlet for the ventilation of the drain, shall be properly trapped. By-law 66 specifies the particular way in which the various waste-pipes from the sanitary appliances within the building, including soil-pipes, shall be dealt with before communicating with the drain. It is our purpose in this chapter to deal with the whole of these pipes seriatim.
The last paragraph of By-law 62 implies that even rain-water pipes shall be disconnected before communicating with the drain. For many years it has been the custom in many northern towns, notably in Manchester and Leeds, to have direct communication between the rain-water pipes and the sewers. The evils and disadvantages of this -\-tem have already been pointed out, and as it is clear that the rain-water pipes should discharge into a properly trapped apparatus, it is necessary to consider which is the mast suitable for the purpose. Where a rain-water pipe discharges in a garden, or a yard not affected by traffic, an ordinary self-cleansing gully will meet all requirements. Some of these are specially made with an inlet bend to receive the rain-water pipe, as shown in Fig. 351. Fig. 352 shows Hellyer's well-known rain-water "shoe". This is made without a trap, and unless the branch-drain has an interceptor before being connected to the main-drain, a P or S trap should be fixed at c. In the streets of towns, a stronger gully is required, and one that will take up little space, and, when set, will be flush with the surrounding pavement and free from projections. Cast-iron is the only suitable material for this type of gully. Fig. 353 shows a rain-water disconnecting gully designed by me, which will be found to meet all these requirements. The gully is divided into two compartments by a mid-feather, the rain-water pipe l>eing connected to an union E, which may be either square or round as required, and which leads to the water-compartment of the trap. One half the cover is solid, and lies over the water-compartment; the other half has ventilating openings, and any dirt which passes through is deposited in the dirt-compartment beneath. The size of this gully is only 10 inches by 6 inches, so that if the rain-water pipe is recessed in the wall it takes up little space. In periods of dry weather rain-water gullies should be frequently inspected to see if the seal has been lost by evaporation, and they should be replenished with fresh water as often as required
Fig 351 - Cliff's Rain water Intercepting Gully.
Fig. 352 - HellyerRain-water "Shoe".
Fig 353 - Spinkle's Cast-iron Rain-water Disconnecting Gully.
The first paragraph of By-law 66 prohibits any drain-inlets within buildings, except inlets from water-closets; the object of this clause is to effectually prevent the passage of drain-air into buildings. The mere fixing of a gully-trap in a cellar floor which requires to be drained, is no effectual protection against the inroad of sewer-gas into the house. In the first place, the water-trap in the gully may lose its effectiveness through evaporation. Many of these gullies have very little depth of seal, and when the seal has vanished, the foul air from the sewer or drain passes freely into the house, as shown in Fig. 354. In addition to this, it is now well established that water standing in a trap will absorb sewer-gas, and give it off inside the house. Mr. Joseph Parry, M.Inst.C.E., the water-engineer of Liverpool, in his l)Ook on "Water", page 129, gives the following results of some experiments on this subject: -
"(l) That sewer-gases will pass through waiter. Some interesting experiments on the passage of gases through traps were made a few years ago by Dr. A. Fergus of Glasgow. At the outlet-end of a trap (a bent tul>e), he placed a small vessel containing the test solutions, at the bottom of the S-trap, and test-papers at the top of the S-trap; the test-papers were suspended.
Fig. 355 - Plan and Section of Areas, & c for Cellar-drainage.
He found that ammonia passed through the water in from fifteen to thirty minutes, sulphurous acid in an hour, sulphuretted hydrogen in three to four hours, chlorine in four hours, carbonic acid in three hours.
(2) That traps may be emptied by evaporation. If traps are placed where the water is not frequently renewed, or if a house is long unoccupied, danger may arise from this cause.
All drains should terminate outside the building', and in cases where it is necessary to carry off waste water from basements or cellars, - such as where they are used for washing purposes or as stillages for public-houses, etc. - special means must be taken to convey the waste water to the outside of the house, and the gully-trap must be placed within an area deep enough to receive this water, as shown in Fig. 355. In the case of existing cellars already drained, as shown in Fig. 354, it would be expensive to disconnect them in the manner shown in Fig. 355, but the same purpose may be effected by inserting an intercepting trap, and carrying up the air-inlet to the surface, as shown in Fig. 356. It is particularly important that there should be no connection from the drain, even when a gully-trap is provided, to any larder or cellar in which food or milk is to be kept; the provision of a gully for carrying off water used in washing the floor is entirely unnecessary, as cellars can be effectually cleansed by the proper use of a mop.
Fig. 356 - Disconnection of Cellar-drain by means of a Trap and Air -shaft.