(2) Hair traps. Hair traps are installed as waste connections or collections
in lavatories. These traps are manufactured with baffled partitions and screens to keep
hair, lint, and other material out of waste lines. Traps must be cleaned frequently to
ensure satisfactory service.
(3) Plaster traps. Plaster traps are installed in waste connections to sinks
in hospitals, laboratories, industrial plants, and other places where plaster of paris and
other insoluble materials are used. These traps keep foreign material from waste lines.
Material accumulating in the traps must be removed frequently to ensure satisfactory
(4) Gasoline and oil interceptors. Discharging gasoline, kerosene, or any
other volatile liquid into sewers is strictly prohibited. Volatile liquids accumulating in
sewers may cause explosions and destroy sewer lines or the treatment plant. They
also interfere with proper operation of the plant. Signs of gasoline, lubricating oils, or
grease in sewers must be traced to their source. To remove this explosion hazard from
the wastewater collection system, gasoline and oil interceptors built on the same
principle as grease interceptors are installed in drains from garages, washracks, and
shops where greasy wastes are discharged in manageable amounts. The gasoline, oil,
and grease accumulating in the interceptor must be skimmed off at regular intervals to
assure effective removal of the hazard.
b. Structures. A wastewater collection system consists of a collection or group
of sewer pipes, pumps, and other structures, as necessary, to transport or convey
wastewater for treatment and final disposal. These structures include:
(1) Plumbing fixtures. These fixtures consist of sinks, flush toilets, shower
drains, and the like through which waste enters the collecting system. A P-trap (see
Figure 1-3) is important in the construction or installation of a plumbing fixture. Weak
wastewater remaining in the P-trap acts as a water seal between the fixture and the
remainder of the collection system. Accordingly, odors and toxic gases from the sewer
do not escape through the fixture but escape instead through the vent in the house
(2) House sewer. A pipe or pipes connecting the sanitary plumbing
facilities of a single building to a common sewer. A vent pipe which permits wastewater
to flow without siphoning the water seal in the P-traps is included as a part of the house
(3) Lateral sewer. A sewer line connecting to a branch or other sewer and
having no other common sewer tributary to it.
(4) Branch sewer. A sewer that is serving a relatively small geographic
area. Any sewer serving more than one house is termed a common sewer.