Practically all municipalities with populations of more than 2,500 maintain systems of sewage disposal consisting of a sewage treatment unit of either activated sludge or filter type and a system of sewers installed below the streets by which the raw sewage is conveyed to the disposal plant or unit.

In recent years health authorities have realized more than ever before, that the source of drinking water must be protected against contamination caused by the discharge of large volumes of domestic and industrial sewage into it. With the aid, in some instances, of federal grants, this phase of sanitation has progressed rapidly within the last ten years.

The installation of public steam enclosures doesn't necessarily involve a plumber. Residential steam showers (http://www.mybath.biz/typesofsteamshowers.html) and steam rooms, however, are a new field into which he may easily be fitted. As far as the installation of public sewers and disposal units is concerned he does not play a very active part.

The work, especially that of constructing concrete and vitrified clay sewers, usually is done by semi-skilled labor or by workers trained in this field. The plumber does, however, use the public installation as a terminal for private plumbing systems, and it is quite necessary that he should be familiar with the public system, at least to the extent of being well-informed.

It is quite essential, too, that he know the various types of sewers and the principles involved in construction and operation of a modern disposal plant. There are three types of public sewers, each classified according to the kind of wastes it is required to handle.

Combination public sewers are the oldest variety of the three types of sewers and they are required to carry storm and sanitary wastes to some safe terminal. These sewers are obsolete, but still make up a large part of public sewage systems. Rain water should be carried to some terminal not associated with the disposal plant, because large quantities of water affect operation and necessitate an exceptionally large installation to handle it.

Water from your bathroom, from either the toilet or the bathtub (http://www.mybath.biz/servlet/the-265/Rainforest-78-Steam-Shower/Detail) can go here. Bathtub paint tends to cause some problems with drains so make sure you keep up with glazing.

Sanitary sewers are those which are required to carry domestic sanitary wastes only. All rain water must be excluded from them. The terminal of these sewers is a modern sewage disposal plant. Combination and sanitary sewers generally are placed about ten feet under the street grade and usually are found below the center line of the street.

Storm sewers are a comparatively new installation, made necessary because of sewage treatment. These sewers are made to carry only storm water and may terminate at any natural drainage area.

Although these are meant for large quantities of water, you cannot dump water from your swim spa or hot tub (http://www.mybath.biz/besthottub.html), because the hot tub chemicals need to be disposed of properly. This type of system drains into natural reservoirs and any water that did not come from the sky is contaminated.