Noisy Pipework – Getting to the Root of the Problem
Posted on by Mike Rawlings
Mike Rawlings – Marketing Manager – Soil & Drain Business Saint Gobain PAM
If as an industry we are to overcome the issue of noisy pipework, we need to ensure that we are all measuring the correct problem. Unfortunately while BS EN 14366 defines how noise should be measured, these tests do not measure where the most noise is generated in a system.
With this in mind, is it time to review this standard and change the test criteria so that they better reflect a real life installation?
In practice most noise from pipework comes from offsets in the stack and changes in direction through bends, yet the standard only measures water flowing through a vertical pipe.
It is important because people notice noisy pipes and because the UK code of practice does set criteria for sound reduction in different types of buildings. For structural born noises from equipment behind the room these are set at 30dB(A) in the main rooms of a residential property and at 35-40dB(A) for other rooms.
So in an attempt to bring some independent data to the whole issue, an independent laboratory TVVL conducted 200 tests on different waste water systems and combination of noise reduction factors. A flow rate of 3l/s was used, which is equivalent to the flow generated by a WC being flushed.
For bare pipework the noise ranged from 61.0dB(A) for the worst performing pipe material down to 51.0dB(A) for a vertical pipe and from 64.5 dB(A) to 50.5 dB(A) for a horizontal pipe. Measurements were taken at offset points and changes in direction.
The tests were then extended to include noise reduction factors. It showed that if you use both glass wool plus an enclosure constructed from gypsum board, you could reduce the noise (or sound pressure level) by up to 30dB(A) in walls. In ceilings you can reduce the noise by up to 25dB(A).
I would argue that this is significant for two reasons.
Clearly it is time to update the standard BS EN 14366:2004 so that tests more realistically mimic real life installations. Second it really does make a difference in choosing the pipework material to reduce noise – the decibel scale is not linear so a difference of just 4dB is actually twice as loud as the quieter alternative.
For the record the tests found that cast iron was the quietest pipework material.