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Comparative Sound Testing of Cast Iron and PVC Stacks

Noise from DVW pipes in a wall cavities adjacent to living rooms, dining rooms and bedrooms can be annoying when waste water is discharged into the drain pipe from upper floors. In the past, the only sensible option to reduce sound was to use cast iron in place of PVC plastic pipe.

We developed a different solution; a variation on standard PVC piping which will also fit inside a plumbing wall. We performed comparative sound tests with ProVent Shell Pipe, cast iron and standard PVC piping, keeping everything constant except the type of pipe. As sound engineers know, it is difficult to reliably test the soundproofing qualities of different types of piping because a small change in the environment or in attaching or securing the pipe can change the test results.

In order to evaluate the soundproofing capabilities of ProVent Whisper Quiet Shell Pipe, we tested each type of pipe by flushing the same 1.6 GPF bottom outlet water closet within the same mounting frame and using the same attachment method for each type of pipe.

Sound tests were performed in order to detect the actual sound difference between:

ProVent Whisper Quiet Shell Pipe snapped around regular, approved PVC pipe;
Regular, approved PVC pipe without Shell Pipe; and
Regular, approved Cast Iron No-Hub Soil Pipe.
The noise levels recorded were:

Using ProVent Whisper Quiet Shell Pipe around the bare PVC pipe recorded a high of 67 dB
Using bare PVC pipe without the Shell Pipe recorded a high of 76dB
Using Cast Iron No-Hub vertical stack pipe recorded a high of 72 dB
These results are not as close as they appear. A level of 70dB has 10 times the noise intensity of a level of 60dB. These results indicate that the bare PVC pipe registered over 8 times the noise level of the ProVent Whisper Quiet Shell Pipe and that the cast iron pipe registered over 3 times the noise level of the ProVent Whisper Quiet Shell Pipe.

While we expected the Shell Pipe to outperform the PVC pipe, the fact that it outperformed the cast iron was a complete surprise since cast iron has always been known and advertised as the quiet pipe.

Whisper Quiet Shell Pipe (US Patent Pending)

The Shell Pipe is available in 5 foot lengths and will fit into regular wall cavities, can be cut to accommodate any length of regular bare PVC pipe where water noise could be an issue.

The Shell Pipe has tongue and grove joints that snap together and requires two (2) evenly spaced PVC rings per section. The enclosure provides an air space around the bare pipe that creates amazing sound proofing.

There is usually a large space within the drop ceiling so the PVC piping can be protected by using regular insulation, therefore, this portion of piping should not contribute significantly to the water noise.

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