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.
It will thus be seen that sewage can be raised by simple automatic apparatus involving practically no expense in maintenance, in which there are no moving parts, except flap-valve, nor other mechanism to get out of order, and which requires no manual labour or expensive motive-power. The first cost depends upon the amount of sewage to be lifted, the height of lift, and the convenience of the positions for the forcing and air cylinders and the flushing tank, and the amount of labour that will be expended in fixing them, and which will of course vary in every case But the circumstances which affect these, while they may cause the lengthening or bending of some of the pipes, will not impair the efficient working of the arrangement, as they have no relation to the principles on which it is designed.
The third paragraph of No. 66 of the Model By-laws prohibits traps between soil-pipes and drains, and in the new by-laws of the London County Council the same stipulation is provided. There is great divergence of opinion amongst sanitariana as to the value or otherwise of an intercepting trap at the foot of the soil-pipe Those who are familiar with Mr. Hellyer's work, T)ie Plumber and Sanitary Houses, will remember that Mr. Hellyer is a very strong advocate indeed for the placing of an intercepting trap at the foot of soil-pipes, and his book contains a large number of illustrations showing how this plan can be adopted under a great variety of conditions. Another eminent sanitarian, Dr. Pridgin Teale of Leeds, is also a well-known advocate of this system. In the case of a small single house with only one w.c. at no great distance from the intercepting chamber. a second disconnection may not be necessary; but where the branch-drain is of considerable length, a second disconnection is a great advantage, or where there are a number of houses side by side, each connected to a common combined drain, then it is certainly desirable that there should be a second disconnection.
It is the universal practice to fix traps in the waste-pipes from sanitary appliances, and as they have to be disconnected and discharge over a trapped gully in the external air, they are therefore doubly trapped. If this is the right principle to apply to waste-pipes, it is surely right to apply it to the soil-pipe; but as it is not desirable to have the open end of a soil-pipe discharging over a gully, an intercepting trap of special construction has to be adopted with a shaft carried to the surface on the inlet side and finished with a grating. The only possible smell which can arise is when a discharge from the closet is passing through the intercepting trap immediately after use, but as that discharge is very rapid, it is not likely that any smell will be detected. At my own boon, the soil-pipe is disconnected at the foot, and the grating is within a few feet of a door, and is constantly traversed each da 1 have never myself been able to detect the slightest odour, nor have I ever had any complaints whatever. Mr. Hellyer in his book also states that he has one within ten feet of his office window, and has never found it in any degree offensive; and he cites a case which shows that the system can be adopted without being in any degree objectionable. The particulars of this case are as follows: -
"About the year 1882, I had two stacks of soil-pipes fixed with a large number of valve-closets upon each, and they were made to discharge with open ends into open traps. But as the gratings over the tops of the drain 'disconnecting' traps were right in the footway of a narrow public thoroughfare, and as the parties chiefly concerned in the erection of the building would have been too nervous to have sanctioned any such open ventilation, nothing was said about the arrangement of such ventilating traps, and the gratings were supposed by all concerned except myself to be simply covering the ends of rainwater pipes. As a proof of the safety of such arrangement, it may be mentioned that, though the closets upon each of the two stacks of pij)es just referred to have been in great use for several years, though thousands of people have walked over the gratings, and though office-windows are within eight feet or ten feet of them, no one has ever noticed the slightest disagreeable smell from the arrangement. Whenever I have examined these intercepting traps, they have been found quite free from any offensive odour, and the atmosphere has been passing freely into the discharging end of the soil-pipe at this point, and not out of it."
There are, of course, many ways of supplying fresh air to the soil-pipe without placing the inlet immediately upon the surface of the ground or adjacent to any windows or doors.
Where the disconnection of soil-pipes is adopted, it is necessary to haw in independent ventilation-shaft for the drains, and if the branch from the soil-pipe to the main drain is of suitable length, then a separate ventilator should be placed immediately below the intercepting trap to take the pressure of the foul air from the intercepting trap. It will be generally found that the water standing in the intercepting trap is practically clean water, being the remainder of the flush which has carried forward the soil, and that if any smell is detected escaping through the air-inlet, it will most likely arise from a stoppage in the drain, and is really a warning that something is wrong and requires attention.