This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
284. The problem of disposing of the sewage matter from schoolhouses is sometimes a difficult one, especially where no water supply is available for water closets. A system designed to meet the wants of such cases has been introduced within recent years under the name of the dry-closet system. This should not be confounded with the well known dry-earth system, which is quite unobjectionable on sanitary grounds.
This dry-closet system is operated by an aspirating chimney, usually the same one which draws the foul air from the schoolrooms. The closet seats are located in the roof of a tunnel leading to the chimney, and each seat is provided with a cover which is intended to be kept closed when not in use. The liquids are sometimes drained off, but the solid matters remain on the floor of the tunnel, and are gradually dried by the current of air which passes over them to the chimney. At the end of the school term, the deposits are saturated with kerosene, and then destroyed by fire.
The foul air from the schoolrooms is drawn directly through the tunnel; consequently, whenever a blow-down occurs, not only will the foul air be driven back into the rooms, but the noxious effluvia of the tunnel will be carried back with it.
As drying and evaporation can take place, in this case, only by absorbing heat from the air-current, it is evident that the temperature of the foul air will be lowered somewhat, and the draft of the chimney will be weakened correspondingly. Sometimes a small grate fire is maintained at the entrance to the tunnel or the base of the chimney, to maintain the draft in mild or warm weather, when the heating apparatus is not in use.
In some cases, a separate chimney is provided for the dry closet, and the air is taken only from the room containing the apparatus. The result of a blow-down, however, is the same as in the previous case, except that the communication with the interior room is a little less direct.
The seats in these dry closets are always at a higher level than the inlet for air; consequently, the effluvia in the tunnel always tend to flow out into the room whenever a cover is raised. Usually the chimney draft is sufficient to counteract this tendency and prevent any outflow, so long as only one or two covers are opened; but when all the seats are in use at the same time, as often happens, at recess and other occasions, the draft is wholly inadequate. It is then found that while air flows inwards at a few of the seats nearest the chimney, the vile tunnel air flows out unchecked at the others.
285. Another very serious objection to this system is that much of the fecal matter is reduced, by drying, to the condition of dust, and is carried up the chimney. If this matter happens to be infested with the germs of contagious diseases, these also are dried and projected into the atmosphere. In fact, matter is thus carried into the air that ought to go into the earth. All dust eventually descends to the level at which people breathe; thus, the effect of this apparatus is to disseminate filth and disease germs broadcast over the surrounding country. The dry-earth system, in which all fecal matter is mixed with dry absorbent materials, is free from all such objections.
The dry-closet system of heating and ventilating school-houses, as it is done today, is a disgrace; it is one of the worst disease breeders that can be devised in schoolhouse construction.