MIL-HDBK-1191
oversized, packed with a resilient material such as glass fiber or mineral
fiber, caulked airtight, and covered with escutcheon plates where required for
fire ratings. Piping should be supported on both sides of the penetrations
and should not rest on the structure.
23.4.7
Plumbing Noise.
23.4.7.1
Introduction. One of the most common acoustical problems found in
buildings is the noise generated by the water piping systems. Due to its
easily identifiable nature, plumbing noise is one of the most disturbing and
offensive types of noises encountered in building even though the noise levels
are seldom excessively high. Most of the noise from piping systems is
structure-borne, being transmitted along the piping throughout the building
where the noise is re-radiated as airborne noise.
23.4.7.2
Piping isolation. At wall and floor penetrations, water piping
runs should be free from the structure and the opening packed with a resilient
insulation material and fully caulked. Water supply pipes larger than 50mm (2
inches) in diameter should be suspended from the structure on neoprene-in-
shear hangers or floor-mounted on resilient supports. Flexible pipe
connectors will be used to connect the supply and drain pipes to vibrating
units such as garbage disposals, pot, pan and dishwashers.
23.4.7.3
Water pressure and flow velocities. High pressure and high
velocity flow plumbing systems are inherently noisy due to turbulence in the
fluid flow. To prevent the generation of excessive flow noise caused by
turbulent water flow in the plumbing and piping systems located adjacent to
sensitive areas, water pressure should be in the range of 2.8 kg to 3.5 kg per
square centimeter (40 to 50 lbs./square inches).
23.4.7.4
Water hammer. The use of short, air filled branch pipes or stubs
to control water hammer is not effective and should not be used, since the
entrapped air in the stubs soon leaves these chambers by dissolving into the
water. The most efficient means of preventing water hammer is to install one
of the mechanical devices manufactured for this purpose, which employs a gas-
filled stainless steel bellows to absorb the shock of the hydraulic waves by
mechanical compression of the bellows. These devices are available in a
variety of sizes to accommodate most fixture sizes used in buildings.
23.4.8
Isolation of Materials Handling and Transportation Systems.
23.4.8.1
Vertical services. Chutes, pneumatic tubes, and vertical
conveyors should not be located adjacent to any acoustically sensitive space,
and should be resiliently isolated from the building structure at each floor
penetration by means of rubber-in-shear or glass fiber isolators providing a
minimum static deflection of 12.5mm (0.5 inch). The exterior of each trash
chute and large pneumatic tube should be coated with a visco-elastic vibration
damping compound or other damping material.
23.4.8.2
Other services. Wherever possible, other vertical and horizontal
systems runs, such as pneumatic tubes, conveyors, and monorails should not be
located adjacent to, over, or under any acoustically sensitive space. These
systems should be isolated from the building structure by resilient hangers,
isolated support traps, or resilient pads or trapeze hangers, and should have
no direct physical connection with the finish ceiling system of the space
below. If the horizontal runs are routed over acoustically sensitive spaces,
pneumatic tubes should be coated with visco-elastic damping compound or other
damping material, such as 25mm (1 inch) thick glass fiber blanket, with an
impervious outer covering, such as metal foil. Alternatively, these system
runs can be boxed in, encased, or wrapped with an impervious barrier material
such as dense plaster, gypsum board, or a 50mm (2 inch) thick glass fiber
material, 6 pounds per cubic foot density, covered with an impervious outer
23-14
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