(8.) Economy both to the general rates and also to individuals in carrying out their connections.
(9.) Where old and defective sewers exist they are often fitted to carry surface water, but are quite inappropriate as sewers.
No rules, however, can be laid down with regard to this question, as each town or district must be treated as the case requires.
In conclusion, I will mention the different methods at present in vogue for the sewerage of towns.
(1.) The combined system, where all sewage, surface water, manufacturers’ refuse, and subsoil waters are carried in the same sewer.
(2.) Similar to the above, the subsoil water, however, being carefully excluded.
(3.) The partially separate system.
(4.) The absolutely separate system, where there are three sets of sewers, one for sewage proper, one for surface water, and one for subsoil water.
(5.) The “Lieurner” system, which professes to remove all sewage by exhausting the air in the sewers and drains.
(6.) “Shone’s” pneumatic ejector system, which is described as follows:—