Reducing drainage noise


Adam Cafer of Polypipe Building Services discusses how sound pollution can be reduced, especially in tall building drainage systems.

With one third of the UK workforce currently working from home, issues such as noise pollution from building service systems will be brought into sharper focus – especially for the growing number of people who live in residential blocks in our major towns and cities.

Modern multi-storey buildings contain a large amount of plumbing fixtures and pipework, and if installed unsatisfactorily the noise of water and wastewater passing through pipes can cause excessive noise for tenants.

There are a number of modern design solutions and product systems available however to help minimise the effect of noise from building drainage systems, without compromising on maximising available floor space to rent, or the robust quality of the products employed.

Meeting the regulations

Part E of the English Building Regulations state that airborne sound transfer between flats must be reduced by at least 43-45 decibels through the separating wall or floor. A level of 20dBA is an acceptable sleeping room ambience, and 80dBA is the level of ordinary traffic, so it is important to specify above the UK standard at the design stage of a development.

While there are no explicit standards that specify the acoustic performance of soil and waste pipes, it is important to adopt a holistic approach when considering the acoustic issues faced by tenants living in tall buildings.

Selecting the correct products when installing a complete drainage system with its related components – and tackling the source of potential noise problems during installation – will help to prevent long-term issues.

Acoustic soil and waste systems are one solution, able to effectively dampen both airborne noise and sound transmitted through the building structure.

Acoustic systems lagged with a minimum of 25mm mineral wool and fitted with acoustic, rubber-lined brackets will reduce the risk of pipes vibrating as water flows through. A triple layer pipe system with specially developed co-polymer polypropylene layers can be used in conjunction with flexible and vibration-resistant joints, support clips and fire collars. The sandwich of a high density sound-reducing material between two layers of polypropylene tackles both wall-borne and air-borne noise.

There are also a number of modern drainage systems which are not designed exclusively for acoustic control but achieve it as a secondary benefit. Many of these systems, which help to ensure low-noise environments, can be installed during the build or retrofitted into tall buildings.

Coping with pressure

A Positive Air Pressure Attenuation system with an air admittance valve provides a drainage ventilation system that helps control nuisance air pressure regimes which otherwise would establish themselves within the soil and waste system as water building, often from great heights.

The positive pressure reduction device is used to mitigate the effects of positive air pressure fluctuations in the drainage pipework system, such as when a WC is flushed on an upper floor.

As water descends down the single stack drainage system, it creates a negative pressure that if interrupted, or is approaching a change of direction, causes the negative pressure to change to a positive pressure which then travels back up the pipe and can create knocking or jolting noises as it passes through the drainage system.

The positive air pressure reduction device acts as an attenuator tackling positive air pressure fluctuations, and the air admittance valve tackles negative air pressure fluctuations. Therefore by installing these two components into a single stack it is possible to significantly reduce pressure fluctuations, and eliminate the requirement for secondary ventilation.

Designing the secondary vent pipework out of the system saves material and labour, creates space in the living area, reduces core drilling of the slab and means no venting through the roof, thus reducing the risk of leaks.

Controlling the air fluctuations also has the added benefit of considerably reducing the noise created throughout the system whenever water from WCs baths, showers, sinks and kitchen appliances is released.

Together, the positive air pressure reduction device and the air attenuator form a highly effective alternative solution for controlling the air fluctuations and the noise pollution within the single stack drainage system and soil stack, thereby protecting the water trap seals of appliances within the building.

Holistic solutions

Employing a single stack system allows for the use of less pipework, while maximising the available floor space within the building structure.

As the quality standard of residential tall buildings rises, it is important to look for holistic solutions designed to reduce acoustic disturbances.

If you liaise with an experienced and reputable manufacturer, you will be able to receive technical and specification guidance, ensuring a high-quality, properly engineered installation.

Adam Cafer is Advantage technical manager at Polypipe Building Services