Q. Will you please illustrate the proper way to drain cellars, and the manner of connecting with the main drain leading to the sewer? What precautions should be used to prevent sewer-gas backing into the cellar, presuming that water passes from the cellar into the drain only during fall and spring - cellar being dry during summer and winter?

Figure 33.

A. The annexed cut shows how the ground-drainage can be delivered to the house-drain with little risk. It is supposed that the building stands by itself, and the ground-drain is to be laid quite around the foundation of the house. If so, it will effectually cut off all water that might otherwise make the cellar damp. It is also supposed that the soil-pipe extends up through the roof in all cases. This insures an inward draught at the vent-hole where the ground-water is admitted, so that the air from inside the house-drain is not likely to follow the ground-drain, which has no vent at its upper end. If rain-water is admitted into the trap as here shown, it keeps the trap flushed occasionally, and it is then better to provide an extra air-hole by a T-branch just above, as shown, so that the air-draught need not be in any way obstructed by a rapid influx of rain-water, as it otherwise might be.

If drainage-fixtures are needed on the level of the cellar-floor, the pipe draining them is laid below that level, as here shown; it should then be kept accessible by building dwarf-walls each side of it up to the level of the floor of cellar, where the trench can be covered with planks or flags of stone, so fitted as to be readily lifted, and not spiked or cemented down. If no water-closets, sinks, or similar fixtures are needed on the cellar-floor it is better to keep the pipe above that level, as shown by the dotted lines.