The building sewer shall be of such size as
required by the approving authority to serve the connected fixtures.
In no case shall the building sewer be less than four inches in diameter.
The building sewer shall be constructed of east
iron. Schedule to PVC, vitrified clay, asbestos cement or other material
acceptable to the approving authority.
All pipe joints of the building sewer shall
be made watertight and protected against damage from roots. Poured-type
joints shall be properly wiped on the inside to present no obstruction
to flow.
The building sewer shall be laid on a firm base.
The building sewer shall be designed to provide
a minimum velocity of sewage flow of two feet per second when flowing
full. This requirement is met when a four-inch building sewer is laid
at a slope of not less than 0.01 (1/8 inch per foot). A slope of 0.02
(1/4 inch per foot) is desirable.
The building sewer shall be laid on a continuous
grade and as nearly as possible in a straight line.
Manholes, with metal frames and covers at grade,
shall be provided at the junction of two or more sewers and at intervals
no greater than 300 feet, except that manholes will not be necessary
where building sewers join lateral sewers if a long radius bend is
provided. All gravity sewer manholes shall have an open channel depth
equal to or greater than the diameter of the inlet sewer, and the
change of direction in each manhole shall not exceed 90° (change
of direction of flow and imaginary extension of the original direction
of flow).
The building sewer shall be vented through the
vent stack or main vent of the building served by it, and no trap
shall be installed in the building sewer or building drain.
