Plumbing And Piping Noise

Noise from plumbing and piping is one of the most important causes of dissatisfaction in residential structures. It has become much more noticeable with the unfortunate use of plastic pipe in waste stacks, but it can also be caused by excessive flow velocities in supply pipes and be exacerbated by poor isolation. Plumbing and piping noise frequently originates with turbulent flow in pipes and fixtures and is transmitted primarily through vibrational coupling to the building structure and into the occupied spaces. Several other noise generation mechanisms are present in plumbing including cavitation, water hammer, vibrational transmission of pump or other mechanical noise, and water impact or splash noise; however, noise produced by turbulent flow is the primary source.

Supply Pipe

For normal velocities, the flow of water in straight residential supply pipes can be considered to be turbulent. In turbulent flow, regions of highly varying pressure are created, which transfer to the walls of the pipe and from there to the structure. Although turbulence is present in straight pipe, it is mainly caused by valves, fixtures, elbows, and constrictions. Several factors influence the noise generated by a supply pipe. The first is the velocity of flow within the pipe itself, which affects the amount of noise created by any valves or fixtures. The second is the way in which the pipe is attached to the structural framing, both to the structure and to the surface material.

Measurements have been made by Van Houten (1979), who investigated both these factors. Figure 15.15 shows his experimental setup. The test apparatus consisted of a double stud wall with one layer of drywall on each side and supply piping through the studs on the far side of the wall. Pressure was regulated with a valve and the pipe was terminated in a flexible hose. This is perhaps not the most realistic test condition since in a real situation the flow regulating fixture would probably be remotely located.

The attachment methods are sketched in Fig. 15.16. When pipes are routed through holes drilled in a series of studs it is rare that each hole is perfectly aligned with its neighbor. Consequently the pipe, which courses through these holes, will lie closer to the stud on one side or the other at each penetration. Isolators that are wedged into the holes will be pinched on the close side or will be loose if the holes are oversized. The preferred mounting method is to wrap felt around the pipe, outside the hole, and to band it with plumbers tape. This

Figure 15.15 Piping Noise Test Configuration (Van Houten, 1979)

Figure 15.15 Piping Noise Test Configuration (Van Houten, 1979)

Figure 15.16 Pipe Mounting Methods and Descriptions (Van Houten, 1979)

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