Specifier Review

Of sound design

Based on findings from its dedicated acoustics laboratory, Victoria Willis, Product Manager for Geberit, explains the importance of taking a complete system approach to designing out the nuisance sound of sanitary noise.

Good bathroom acoustics requires a holistic approach, beginning at the design and specification stage and culminating in exact installation practices. For a completely satisfactory outcome where no-one is disturbed by sanitary noise within a building every element must be considered; from where the bathroom resides in the building, to the type and configuration of drainage pipes, sanitaryware and how it is installed. Measuring the noise from running water in drainage pipes alone does not give an accurate picture of the overall acoustic levels in real buildings, which is why Geberit has a dedicated sound laboratory at its Swiss headquarters where scientists perform sound measurements on the complete system, inclusive of cistern, WC, wall structure and drainage, under realistic conditions. Such tests and their results enable Geberit to make informed and reliable recommendations for ensuring everyone within a building can look forward to a sound night’s sleep.


Generally, bathrooms should produce no more than 40dBs of noise and in the UK, bathrooms are considered to be performing at a reasonable level when up to 44dB of associated sounds can be heard in an adjoining room. Scientists at the Geberit acoustics lab found that using a combination of Geberit systems sound readings can be taken down as low as 25dB. Thislow sound rating was achieved in two true-to-life test scenarios: In a room with timber stud walls, 15mm plasterboard and timber pre-wall fitted with a wall-hung WC and Geberit Silent-db20 pipework, and in a room with Geberit Duofix metal stud walls, 15mm plasterboard, wall-hung WC s fitted back-to-back and Geberit Silent-db20.

Noise is in the air

Sound travels through the air (airborne) or walls (structure-borne). Airborne sound can be minimised by using insulating material around pipes, for example. Structure-borne sound, which causes sound to travel through a building – a particular problem in multiple-floored buildings incorporating several bathrooms – can be tackled by keeping individual components apart from one another. As a general rule of thumb, installation walls should not border areas that are intended to be quiet, such as bedrooms, while de-coupling the WC from the fabric of the building (both the structural wall and the floor) also goes a long way to ensuring a building is acoustically sound.geberit

It is for this reason that wall-hung sanitaryware is a more effective sound reducing option than back-to-wall or close-coupled WCs, eliminating noise travelling through the floor. Research in Geberit’s own state-of-the-art sound laboratory found that lightweight pre-wall has a significant effect on sound insulation by moving the WC away from the main fabric of the building. This kind of structure can also be given additional sound-absorbing properties using a thin foam layer facing the floor or ceiling.

Frame it

In addition, rubber brackets, elastic connections and insulating layers, can all help to prevent solid-borne sound. A Geberit Duofix frame optimises acoustic values, with integrated rubber tipped push rods to reduce noise from the flush plate when pressed for flushing, a polythene jacket insulating the cistern, circlips on threaded rods to eliminate movement and sound absorbing seals on drainage brackets.

When installing any WC, an insulation mat on the wall, as well as sound insulation sleeves for fastening screws, will also help reduce noise. Geberit insulation tape can be used between panels, system rails and building structures to maximise results.

In terms of piping, always choose pipe brackets with rubber lining and make sure they are not tightened too firmly. Cement should not be used to fasten components to the wall, as this could result in sound bridges. Instead, by selecting Geberit pipe brackets with the appropriate diameter and tightening them fully, optimum fastening and sound insulation conditions can be achieved.


In the pipeline

One of the vital steps to reducing pipework noise is minimising the number of off-sets in the pipe runs. For example, a 45 degree bend creates 9dBs as opposed to just 5dBs from a 15 degree bend. Multiplied by the numerous pipes used within a many-floored building this equates to considerable sound savings.

Where possible choose pipework with integral noise reduction, such as Geberit’s Silent-dB20 which includes stone composite to deaden water sound as it runs through. Geberit Silent-db20 also has sound insulating ribs on the impact zones, further minimising sound development as waste water travels through the pipes.

By taking such a complete system approach to building acoustics, Geberit offers everything needed to reduce noise: a fully integrated system of silent and easy-to-install products as well as specialised know-how in planning and installation. The effect is not only audible, but visible too, because silent Geberit installations are an ideal basis for great bathroom design.

Geberit – 01926 516800 www.geberit.co.uk