Page 543 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch14_500-554.qxd 8/7/10 8:56 PM Page 501

14.1 Drainage of Buildings 501

Caulked pipe sleeve
Fresh-air inlet

Foundation
Street Sidewalk
wall
Vent

Caulked pipe sleeve Cleanout Basement floor

Common or
public sewer
House drain;
cast iron;
House sewer or service slopes 8 in.
1
connection; vitrified tile; House or or more per ft
1
slopes about 4 in. per ft; running trap
not less than 4 in. in diameter,
preferably 6 in. or more
Figure 14.2 Connecting Building Drainage System to Sewer (house trap may be
installed or omitted). Conversion factor: 1 ft 0.3048 m; 1 in. 2.54 cm 25.4 mm

horizontal drains empty into substantially vertical stacks. These, too, must not flow full
if wastewaters are not to back up into fixtures on the lower floors. The drainage stacks
discharge into the building drain, which, 5 ft (1.5 m) outside of the building, becomes
the building sewer (or house sewer) and empties into the street sewer (Figs. 14.2, 14.3,
and 14.4).
Traps are either part of the drainage piping or built into fixtures such as water clos-
ets. The traps hold a water seal that obstructs, and essentially prevents, foul odors and
noxious gases, as well as insects and other vermin, from passing through the drainage
pipes and sewers into the building. Discharging fixtures send water rushing into the
drains and tumbling down the stacks; air is dragged along, and air pressures above or
below atmospheric within the system might unseal the traps were it not for the provision
of vents. These lead from the traps to the atmosphere and thereby equalize the air pres-
sures in the drainage pipes.
The wastewater from fixtures and floor drains below the level of the public sewer
must be lifted by ejectors or pumps (Fig. 14.1). Sumps or receiving tanks facilitate auto-
matic operation. Sand and other heavy solids from cellars or yards are kept out of the
drainage system by sand interceptors, grease by grease interceptors, and oil by oil inter-
ceptors. To act as separators or traps, these generally take the form of small settling,
skimming, or holding tanks.
Cast-iron, galvanized-steel or wrought-iron, plastic, brass, and copper piping are em-
ployed for drains and vents aboveground; cast iron and plastic are used for drains laid
belowground. Building sewers are constructed of vitrified-clay, plastic, or cast-iron pipe.
Stormwater from roofs and paved areas taken into a property drain is discharged into the
street gutter or directly into the storm sewer. In combined systems, roof water may be led
into the house drain and water from yard areas into the house sewer. Otherwise, storm
runoff travels over the ground, reaches the street gutter, flows along it, enters a stormwater
inlet or a catch basin, and is piped to a manhole, from which it then empties into the
drainage system.