The same effect is often produced by a neighboring building or a border of trees that are higher than the chimney and dense enough to effect the wind pressure. CHAPTER VI PLUMBING The term plumbing is usually understood to cover all piping and fixtures that carry water into the house and remove the waste material in the form of sewage. It does not include the pipes of the heating system. Although the work of installing heating plants is frequently done by plumbers, pipe fitting and plumbing are two distinct trades. In the process of building a house the rough plumbing is put into place as soon as the structure is enclosed and the rough floors are laid. The rough plumbing includes the soil pipe, into which the waste pipes from the various fixtures empty, and those pipes which must occupy a position inside the partition walls and beneath the floors. The connections here described are for a city dwelling and apply to the custom of local conditions. The same system might be used for a country residence except in regard to the water supply and method of sewage disposal. Plants of this type are discussed in the chapter on _septic tanks_. Fig. 58 shows a cross-section of the street, exposing the sewer _S_, the water main _W_, and the connections with the house. The side of the house has been removed to permit a view of the water and sewer pipes, connecting with the bathroom, kitchen, laundry and other basement fixtures. The lateral sewer or house drain, which connects the house with the street sewer _S_, is provided with a trap _G_, located, in this case, just outside the basement wall. The house drain is made of vitrified tile, laid so as to grade into the street sewer with the greatest possible pitch. The sections are laid as true as conditions will permit and the joints are all carefully filled with cement mortar to prevent leakage. The object of the trap _G_ is to prevent sewer gas from entering the house from the main sewer. The trap prevents the gas from passing because the water in the bend of the trap forms a water seal, beyond which the polluted air from the sewer cannot travel. [Illustration: FIG. 58.--Cross-section of a city street showing the watermain and sewer pipe with their connections to a dwelling.]