Plumbing – tales of the unexpected

by FM Media
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An occupant’s expectations within a building or facility have a significant impact on their overall experience. For example, if the hot water in the shower is operating as it should, nobody complains and it is simply business as usual.

However, an unexpected experience caused by the plumbing system can have a significant impact on the continuity of any business.

The operation of any plumbing system within a building generally goes unnoticed, almost taken for granted – at least the majority of the time. A recurring overflowing toilet, shower running out of hot water or poor water pressure can all influence how well a building or facility performs.

In the majority of cases, these occurrences can be prevented. However, unwelcome noise within the facility’s plumbing system is construed as a nuisance. So how can this pose a significant risk to the tenants of the building or facility?

Erbas & Associates' Paul Angus

Erbas & Associates’ Paul Angus

Customer satisfaction is crucial to any business. Research indicates that a satisfied occupant within a building or facility will be more likely to share their experience in a positive manner. However, a dissatisfied occupant is more likely to inform a considerable number of friends and colleagues of their experience. Unfortunately, there is a trend to tell their story on social media, which can have a disastrous effect, leading to a tenant ending their lease prematurely and loss of revenue to the business.

Unwelcome noise is a nuisance. Excessive noise experienced in the plumbing system that is transmitted from another part of the building can often be considered as highly intrusive. In an existing facility, this can be one of the most difficult sounds to alleviate without major repercussions.

A high degree of noise transmission can be tolerated if confined to local usage, for example, if you are the one instigating the noise. However, noise transmitted from another dwelling or part of the building, resulting in an interruption to another occupant’s well-being, is an annoyance. More often than not it will result in a complaint being made and potentially a costly exercise to provide corrective measures within an existing facility.

I still recall the first occasion when I experienced an unexpected encounter with a noisy plumbing installation. Earlier in my career as a service engineer, I spent one week every month travelling around the UK, predominantly focusing on and around London.

Bleary eyed and exhausted after sitting in long traffic jams on the notorious M25 in rush hour traffic between appointments, I finally checked in to the hotel. I proceeded to quickly jump in the shower to get refreshed and grab a bite to eat, before falling into bed to get some much needed rest and recuperation for the next day.

On this occasion, it was a cold, wet and windy winter evening in Brighton, south England. I was staying in a very old, art deco style hotel, dating back to the early 1900s. The hotel itself was eerily empty, with only a few guests, who were nearly as old as the hotel itself. I was suddenly awoken at three am by the sound of a toilet being flushed in the room above me, probably the elderly couple I had noticed earlier.

Then, just as I was getting back to sleep, the noise of the WC being flushed reoccurred, with the wastewater whooshing within the pipework and reverberating throughout the room. I was now wide awake from my deep sleep.

As I was cursing the couple in the room above me for flushing their toilet (not once but twice), I was now racking my brains for why the plumbing pipework configuration in the hotel room above would be designed so badly, with absolutely no thought on its acoustic performance to the occupant of the room.

So when does a noise become an issue? The average WC or shower when operating produces around 75 to 85 decibels (dBA), when confined to the amenity area itself.

In Australia, the method and arrangement of establishing the sewer and wastewater pipework diameters and velocities should conform to AS 3500.2:2003 Part 2, Sanitary Plumbing and Drainage, as referenced by the National Construction Code (NCC).

In addition to the NCC, AS 717.1 2004: Acoustics – Rating of sound insulation in buildings and building elements: Part 1 – Airborne sound insulation, and Part 2 – Impact sound insulation, make provisions to ensure that the acoustic performance of the plumbing system is carefully considered.

As mentioned within the CIBSE (Chartered Institution of Building Services Engineers) Guide G, 2014, public health and plumbing engineering, the location of the pipework, as well as how the space is being utilised, are all relevant to the acoustic performance. For example, if the horizontal pipework at high level is located within the car park of the building, the pipework material and acoustic requirements will be minimal.

For areas where noise is potentially an issue, such as office tenancies, residential areas or hotels, acoustic pipework treatment will be necessary to limit the noise to around 40dBA. This can be undertaken in a variety of ways, such as insulating the riser or pipework, installing pipework with a superior mass in comparison to unplasticised polyvinyl chloride (uPVC) pipework, or alternatively locating amenities and associated pipework away from noise sensitive areas.

An acoustic consultant can assess and provide expert advice to any potential noise impact within a building or to the occupants of a particular area of the building.

Wastewater and sewer pipework conveys the discharge from the sanitary appliances through the building to connect to the main discharge stack, located within a riser. The location of the riser is paramount to ensure it is not penetrating a noise sensitive area of the building.

Architects have a tendency to limit the number of risers within buildings, which has an adverse effect on the amount of offsets and long horizontal runs of high-level pipework within the plumbing system. Noise can be transmitted from a fixture reverberating quite a distance throughout the building if designed and installed incorrectly.

The sound of wastewater conveying though the sewer pipework can be transferred directly from the surface of the pipework as airborne sound. This can then reverberate throughout the building structure in any instances where the pipework is not isolated from the surfaces, for example, via the pipework support or the pipework connected to the appliance being operated.

As well as airborne noise within the drainage system, structure-borne sound issues may be dealt with utilising the building’s mass and insulation properties. Structure borne sound can be extremely complex to address. In order to reduce potential problems, the number and location of bends within the drainage system should be minimised, while any direct contact between the sewer drainage pipework and structure should also be prevented.

Noise in the normal day-to-day operation of plumbing systems is not only restricted to drainage systems either. For example, on a new state-of-the-art police station facility occupants were complaining of a random high-pitched noise occurring after a few weeks of occupying the building.

After numerous attempts by the contractor to locate the noise, we were engaged to provide independent expert advice. Unfortunately, the noise could not be replicated at the time of the inspection. By interviewing a number of occupants, the noise was understood to be most prominent within the basement car park.

The only operational plant within the basement was the stormwater pump; however, this had been reviewed by the manufacturer on a previous occasion and understood to be fully installed, as per the manufacturer’s requirements with no issue. All the pipework was cast in the slab, as well as within the external wall cavity, so could not be inspected.

Further investigative works with other occupants revealed that they could hear the noise at the ground floor reception areas, as well as outside the building, which seemed peculiar. The only hydraulic related items located externally were the fire hydrant booster assembly, domestic cold-water meter and the gas meter.

Even more unusual was the noise was only being experienced between the hours of five and seven am. This coincided with the shift patterns and naturally narrowed it down to frequency of showering being a domestic water supply pressure related issue.

From assessing the utility water pressure and flow, and incoming water supply pipework diameter valve arrangement we identified the pressure reduction station required maintenance to remove any debris or be replaced as being faulty in operation.

The noise originating from the faulty pressure relief valve (PRV) was transmitting along the copper pipework, located in an external enclosure, which was being reverberated via the water services pipework supports. It had not been installed with the rubber inserts, plus the pipework penetrations had not been sealed between fire compartments between the building, which all contributed to the noise being amplified and being most audible within the basement.

Minimising unnecessary noise in the plumbing system does not have to be complex or expensive. A simple and common sense preventative approach to avoid sound transmission in plumbing systems involves:

  • acoustically treating any horizontal drainage pipework, water supply pipework and stormwater pipework located within ceiling spaces and risers (as an alternative measure, the ceilings or risers containing the pipework should be acoustically treated, along with any penetrations)
  • installing pipework insulation in accordance with the manufacturer’s requirements and making sure it contains no gaps
  • not bridging flexible pipework connections to ensure no noise transmits past the flexible joint
  • minimising any bends in the pipework (should bends be required, 90-degree knuckle bends should be avoided and replaced with long radius bends or two 45-degree bends)
  • reviewing the pipework diameters and velocities in accordance with AS3500
  • avoiding chasing pipework into common shared walls between dwellings, and
  • considering the use of new technologies, such as acoustically sound pipework, which can be installed without the requirement of pipework insulation.

Paul Angus is the hydraulic and fire discipline leader at Erbas and Associates. He has strong commercial and technical capability in developing and delivering hydraulic design strategies and solutions. For more information, contact:

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