Building Design and Construction Handbook - Merritt - Ventech!

14.38 SECTION FOURTEEN
hub; threaded pipe, 12 ft; copper tubing, 10 ft. Supports also should be provided
at the bases of stacks.
Consideration should be given to the possibility of building settlement and its
effects on vertical pipes and to thermal expansion and contraction of pipes, especially
when the pipes have a high coefficient of expansion or are made of copper.
Clean-outs. A clean-out is an opening that provides access to a pipe, either
directly or through a short branch, to permit cleaning of the pipe. The opening is
kept plugged, until the plug has to be removed for cleaning of the sewer. In horizontal
drainage lines, at least one clean-out is required for each 100 ft of pipe.
Clean-outs should be installed at the base of all stacks, at each change of direction
in excess of 45�, and at the point where the building sewer begins. For underground
drainage lines, the clean-out must be extended to the floor or ground level to allow
easier cleaning. Clean-outs should open in a direction opposite to that of the flow
in the pipe, or at right angles to it.
In pipes up to 4 in, the clean-out should be the same size as the pipe itself. For
pipes larger than 4 in, the clean-out should be at least 4 in in diameter but may be
larger, if desired. When underground piping over 10 in in diameter is used, an
access hole is required at each 90� bend and at intervals not exceeding 150 ft.
14.14 WASTE-PIPE MATERIALS
Cast iron is the most common pipe material for systems in which extremely corrosive
wastes are not expected. Polyvinyl chloride (PVC) is often used because it
is inexpensive, lightweight, and easy to install. Galvanized steel, copper, and acrylonitrile
butylene styrene (ABS) also are used.
Plumbing piping should conform to one or more of the accepted material standards
approved by the plumbing code applicable in the area in which the building
is located.
For cast-iron pipe, the fitting joints are calked (with oakum or hemp and filled
with molten lead at least 1 in deep), push-on which use rubber gaskets inserted
into the bell of the pipe, or are no-hub (drawn stainless steel bands with neoprene
gaskets). Copper pipe is commonly soldered or brazed, while steel and wroughtiron
pipe have screwed, flanged, or welded connections.
When planning a plumbing system, designers should check with the applicable
code before specifying the type of joint to be used in the piping. Joints acceptable
in some areas may not be allowed in others.
14.15 LAYOUT OF WASTE PIPING
Sanitary sewer systems should be sized and laid out to permit use of the smallestdiameter
pipes capable of rapidly carrying away the wastewater from fixtures without
clogging the pipes, without creating annoying noises, and without producing
excessive pressure fluctuations at points where fixture drains connect to soil or
waste stacks. Such pressure changes may siphon off the liquid seals in traps and
force sewer gases back through the fixtures into the building. Positive or negative
air pressure at the trap seal of a fixture should never be permitted to exceed 1 in
of water.