WATER TREATMENT, DRAINAGE & PIPED SERVICES
Helping silence a storm: the role of a building’s acoustic rainwater system
James Roper, head of product portfolio at pipes & fittings specialist Aliaxis, looks at how modern technology is being used to provide plumbing that can cope with extreme weather and create comfortable living and working environments
A
s increasing freak weather events1
bring heavier
rain, storms and flooding, buildings need to be prepared for a sudden deluge and the inevitable
noise that comes with it. According to the World Health Organisation,
regular exposure to excessive noise can adversely affect physical and mental health. It can disturb sleep, leading to decreased mental performance, and has even been linked to cardiovascular issues and hearing problems.2 A sound reducing drainage system is
therefore important for multi-storey and multi-occupancy buildings, where design and products are needed to reduce the noise created by not only soil and wastewater but also excessive rainwater. Maintaining appropriate noise levels is critical for the wellbeing and comfort of the occupants of any building. This is of particular importance in settings such as healthcare, education, accommodation and hotels. While insulation is often seen as the primary solution, the drainage system also plays a significant role in mitigating noise pollution.
Most acoustic drainage systems are designed to focus primarily on reducing noise from soil and wastewater, however, rainwater drainage systems are equally important and can often be overlooked. This is particularly important where rainwater pipes are routed internally; a practice that is becoming commonplace in modern buildings. Traditionally, the roofs of commercial buildings
are fairly flat because the pitched roofs seen on residential buildings aren’t practical for the square footage that larger properties need. Therefore, a rainwater system is needed that can offer sufficient run-off to prevent water ponding, while also carrying the water away in a controlled and quiet manner. It is the same principle for soil and wastewater. Acoustic disturbances within drainage systems can be broadly categorised into two types: airborne noise and structure-borne noise. Airborne noise is generated by the movement of wastewater or rainwater through pipes. In these instances, the use of a properly soundproofed system is essential to contain the noise within the drainage infrastructure, preventing it from escaping into occupied areas of the building.
Structure-borne noise, however, originates
from the pipes and fittings themselves. As water flows it creates vibrations which can be transmitted through the pipe brackets to the building’s structure and manifest as disruptive noise in adjacent rooms. To mitigate this, it is crucial to implement a system of brackets and fittings specifically designed to minimise the transmission of these vibrations, ensuring that acoustic disturbances are kept to an absolute minimum. In terms of regulation, noise within the built environment is closely monitored, with clear standards for both outdoor and indoor environments. Outdoor noise, as defined by European Directive No.2002/49/WE, should generally not exceed 60dB during the day and 50dB at night in built-up areas. Indoor noise, however, varies according to the type of building and its usage. For example, noise levels in three-star hotel rooms should not exceed 30dB at night, while more sensitive environments such as boarding schools, care homes, and four-star hotels require a lower threshold of 25dB at night. In highly sensitive areas such as intensive care units, the maximum permissible noise level is 25dB at all times, with hospital patient rooms requiring a limit of 30dB during the day and 25dB at night. It is also worth noting that the height of a building can have a major impact on the resonance of flowing water and the sound transmitted through the fixing system onto the building’s structure. Modern plumbing solutions provide lower decibel ratings than traditional plumbing. PVC products tend to work in the 30-decibel range, while a purpose-designed sound reducing drainage system, such as dBlue, can offer improved noise and acoustic vibrations to a level of 18 decibels at 4 litres per second, with a lower 16 decibels if the Phonoklip bracket is used, which helps to reduce structural born noises. In context, a loud conversation can emit 30db, while a car alarm can hit 90dB. The acoustic benefits of modern pipe systems
are grounded in the science of material engineering. By combining plastics and mineral fillers, today’s pipe construction is designed to significantly reduce the noise generated by water flowing through the pipework. These benefits are achieved through the use of specialised materials, multi-layered pipe structures and precise installation techniques.
For instance, polypropylene (PP), a dense yet flexible material, plays a key role in absorbing sound due to its softer composition. When reinforced with mineral fillers, the acoustic performance is further enhanced. The lightweight dBlue system is made from PP and uses a triple-layer design to provide partial absorption of sound waves helping to significantly prevent transmission of acoustic vibrations between pipes and fittings. It was subjected to a test procedure on the level of noise reduction, conducted at the Fraunhofer Institute in Germany, according to EN 14366. Used in conjunction with the Phonoklip, the dBlue acoustic system is designed to reduce noise and acoustic vibrations to a level of 16dB at 4 l/s discharge rate.
During the specification and installation of
a project, it helps to have a manufacturer’s technical team on hand to advise and assist with any technical requirements, especially providing sizing calculations for flat roofs or balconies to work out drainage requirements and the size of internal pipe systems. Correct installation also means that lagging is required to cut down on noise and condensation. Current building regulations state that all pipes are lagged when passing through habitable space, but this does not currently take into account the enhanced performance acoustic systems offer over traditional solutions. Our product specialists and technical support team have a range of expertise so they can advise on bespoke projects, design, specification and installation, including lagging, and can also make site visits at any stage of a project to offer further guidance. It is clear that extreme weather events are testing every aspect of our infrastructure, with rainwater systems under particular pressure. However, modern technology and manufacturing is helping put a dampener on the noise created by running water, providing a better environment for people in multi- occupancy and commercial buildings.
1.
https://www.greenpeace.
org.uk/challenges/
climate-change/climate-change- extreme-weather/#:~:text=Only%20 rarely%20do%20we%20face,more%20 wildfires%20than%20ever%20before
2.
https://www.who.int/europe/health- topics/noise#tab=tab_1
24 BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2025 Read the latest at:
www.bsee.co.uk
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