No form of trap which depends for its seal upon
the action of movable parts or concealed interior partitions shall
be used for fixtures.
Each fixture shall be separately trapped by
a water-seal trap placed as near to the fixtures as possible, except
that a set of not more than three laundry trays or a set of two laundry
trays and one sink may connect with a single trap, provided that the
trap is placed centrally and the branches connect into the trap seal
at an angle of not more than 60° to the vertical arm. No fixtures
shall be double-trapped behind the house trap.
Each fixture trap shall have a water seal of
not less than 1 1/2 inches and not more than four inches, except
grease traps.
All traps shall be set true with seals and protected
from frost and evaporation.
The bodies of cleanout ferrules shall be made
of standard pipe sizes and material known as "extra heavy" and with
heavy brass screw plugs, with a solid square or hexagon nut not less
than one inch high and 1 1/4 inches in width.
A cleanout, easily accessible, shall be provided
at the foot of each vertical waste or soil stack. There shall be at
least two cleanouts in the house drain, one at or near the base of
a stack and the other, with full-size Y-branch, inside the wall near
the connection between the house drain and house sewer.
All underground traps and cleanouts of a building,
except where cleanouts are flush with the floor, and all exterior
underground traps shall be made accessible by manholes with heavy
iron, concrete or flagstone covers.