How-to: Ventilate a Septic Tank

Smelly Septic Tanks and Septic OdoursMaxi-Filtra sample installation

Unless you are on mains drainage, your septic tank collects all the wastewater from your house. It has no moving parts and just sits there quietly in your garden or yard. Its presence should be unnoticed, but as it needs to be vented, unless a suitable filter is used, nasty smells often surround it and spoil enjoyment of the outside space.

Eliminate smells from your septic tank with the Maxi-Filtra

The following short video features our very sturdy Maxi-Filtra filter, which is designed specifically for outdoor applications to eliminate bad odours. Its robust design means that the Maxi-Filtra can be used vertically or horizontally, and can also be installed in hard-to-reach places.

Studor® Maxi-Filtra™ from Studor on Vimeo.

The Maxi-Filtra is supplied with one carbon filter and a universal connector. It fits 90mm venting pipes without the connector and 75mm/110mm with the connector.

To fit, remove the active carbon filter from its packaging, insert into the body of the Maxi-Filtra, clip on the cap and simply push into the vent pipe. The full installation instructions can be downloaded from our product page.

The active carbon filter operates as a two-way vent, filtering air in both directions. The optional Aluminium Cover provides protection for the Maxi-Filtra when it is installed outside in the open air – it gives added insulation against extreme temperatures (-20°C to +60°C) and protection from animal/birds and the environment, i.e. inclement weather and the sun’s ultra-violet rays.

Maxi-Filtra case studyMaxi-Filtra

Click here to read a previous blog which provides an overview of how the Maxi-Filtra solved the problems of Di Hubbard with her properties in both the UK and Spain.

More information about the Maxi-Filtra can be found here.

 

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Safety and Design

Do you manage the risks of scalding and burning in your building or business? If so, have HSEyou considered the risk of scalding from hot water passing through the water trap beneath the sink?

The UK Health and Safety Executive (HSE) states that there is a risk of scalding and burning if a surface is above 43°C. Serious injuries and fatalities have occurred by contact with hot surfaces such as hot pipes, water traps and radiators; this is where inadequate insulation or design consideration is often not in place.

This HSE guidance is particularly relevant within health and social care environments, as there are greater burn and scalding risks associated with vulnerable people. These risks are linked to children, older people, people with reduced mobility and people with a reduced mental capacity.

Heat Test Scalding - Ketal

The Studor Trap-Vent provided a surface temperature reading of 20°C

Under test, when boiling water was poured into the sink, anonymous metal bottle traps provided a surface temperature reading of 91°C, whilst the UK’s leading plastic trap equivalent registered 73°C – both types therefore providing a high risk of scalding and burning.

By contrast, under the same test conditions, the Studor Trap-Vent provided a surface temperature reading of 20°C – significantly below the temperature which provides a risk of scalding and burning.

These tests are illustrated in this video which explores the ‘fitness for purpose’ of these three product types with the use of a thermal imaging camera – the settling surface temperature of each was recorded 3 minutes after boiling water had been poured into the sink and had passed through the trap into the drainage system.

Potentially dangerous temperatures can be clearly seen by observing the white coloured thermal radiation given off through the camera.

If we consider a vulnerable person, there is a significant risk that they may be scalded or burnt through contact with a metal or standard white plastic trap.

The HSE states:

Scalding and burning water traps, trap ven

There is a risk of scalding and burning if a surface is above 43°C.

‘Many radiators and associated pipework are likely to operate at temperatures that may present a burn risk. Where assessment identifies that vulnerable people may come into prolonged contact, such equipment should be designed or covered so that the maximum accessible surface temperature does not exceed 43°C.’

They’re only going to be washing their hands – how are they likely to have prolonged contact?

Here are a couple of possible scenarios to illustrate how prolonged contact could be a real probability:

  • Someone in a wheelchair wheels up to a wash basin and their knees or legs are in direct contact with the trap.
  • An elderly person has started running the hot tap and then has a fall which results in them being slumped against the trap.

In either of these scenarios, the risk of scalding or burning would be eliminated by installing the Studor Trap-Vent instead of a standard metal or plastic trap. Whilst both the Trap-Vent Compact and Trap-Vent Design gave low readings in the tests mentioned above, the Trap-Vent Design provides even more protection by way of cladding with integrated insulation which surrounds the inner working core.

Eliminating Risk

Installing the Studor Trap-Vent means that should a vulnerable person get close to this fitting, then there is no chance of scalding or burning as the potentially hot trap is completely insulated – something which is quite unique in the industry.

For other benefits and further information about the compact, highly styled Studor Trap-Vent please follow this link.

Here is also an information sheet provided by the HSE: ‘Managing the risks from hot water and surfaces.’

 

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Drainage Ventilation Case Studies

Product Applications and Benefits

Drainage Ventilation Technology. Air Admittance Valves. Drainage Systems

Studor Product Range

In recent months we have significantly expanded the number of case studies available on the Studor website and these are great examples of where the Studor product range can be found in some of the most iconic buildings in the world.

Whilst there are even more reference projects throughout our site, the case studies explore in greater depth the reasons for installing the Studor products; the benefits to the developer, user and inhabitants, as well, in many instances, the cost savings achieved.

The following sample case studies demonstrate the various product applications and associated benefits:

Air admittance valves

Nation Towers – Abu Dhabi

The O2 (Millennium Dome)
Greenwich, London, UK
The Studor Single Pipe System (SSPS), incorporating AAVs and P.A.P.A. (Positive Air Pressure Attenuator), has provided the drainage solution for the innovative and iconic 02 Arena in London, UK.

Ferrari World
Yas Island, Abu Dhabi, United Arab Emirates
The unique design of the Ferrari World Theme Park roof, sporting a massive Ferrari logo, was only made possible using the Studor Single Pipe System (SSPS), an environmentally-friendly and cost effective sealed drainage solution that avoids the need for unsightly roof penetrations.

Ford Field Stadium
Detroit, USA
Installation of Studor Air Admittance Valves (AAVs) avoided the problem of sewer gases entering the Ford Field Stadium (home of the Detroit Lions NFL football team) from the rooftop Air Handling Units (AHUs) which were situated above the concourses.

Pak Tin Estate - Drainage Ventilation Case Study

Pak Tin Estate – Hong Kong

Pak Tin Estate
Hong Kong, China
The Studor P.A.P.A. and Studor Maxi-Vent AAVs have been retrofitted throughout two high rise blocks, each of forty-one floors, on the Pak Tin public housing estate in Hong Kong.

Hamilton Harbour
Queensland, Australia
The Studor Single Pipe System (SSPS) was the chosen drainage solution for one of the fastest selling residential high-rise developments in the state of Queensland.

Nation Towers
Abu Dhabi, United Arab Emirates
The Studor Single Pipe System (SSPS) was specified for installation at Nation Towers, Abu Dhabi, because it allowed for flexibility and simplicity in design whilst also significantly reducing the amount of materials (pipework) used in the drainage system, for a more sustainable solution.

Please keep checking back to our reference projects web page, as we plan to continually expand the case study library to give you further product application examples.

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Multi-national Maxi-Filtra & Mini-Vent

Studor AAVs Prove the Solution in Spain and the UK

Di Hubbard has properties in both the UK and Spain. Coincidentally, both have needed a Studor Maxi-Filtra to solve problems with the septic tanks.

Di herself takes up the story:

Maxi-Filtra 2

Smelly Septic Tank in Spain
“One of our properties is in Spain. The installation has four toilets emptying into a septic tank. In our case, the septic tank was installed without the proper external vent to allow the system to breathe; all we had was a blocked pipe sticking out of the ground and, in time, when one toilet flushed it would suck the water from another in the house and/or fill the toilet bowl without flushing anything.

“We realised what the problem was and immediately unblocked the external vent to the septic tank which, of course, brings its own problems with smell, and so the solution was the Studor Maxi-Filtra.

Mini Vent

Nasty Smells in the UK
“In my UK house I had an AAV on the toilet in my extension because it was not connected to the main stack, so we discussed this with our UK plumber who agreed the solution was to purchase a Maxi-Filtra for our septic tank here too, which we did in 2012.

“Once fitted, the toilets and system started to work perfectly – the filter also removes the nasty smells being emitted from the tank.

“We started to experience the same problem in the last couple of months. The solution was to replace the filter as it has a two year life, and now life is perfect again!

Problem Solving with the Maxi-Filtra and Mini-VentMaxi-Filtra Filter
“We have also purchased the Studor Mini-Vent, as the builders had also plumbed the air conditioning pipes into the sewage system, so each time you ran it the smell of rotten eggs was immediately present in the house.

“Attachment of the Mini-Vent has also resolved this problem, and is a safe solution compared to the alternative use of a piece of kitchen roll stuffed into the pipe!”

All good Studor Solutions! For further details about the Studor Maxi-Filtra or Mini-Vent AAV please click on the product name links or see our website.

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Video: The Studor P.A.P.A. for Multi-storey Buildings

Here is a short video feature which helps explain the features and benefits of the Studor P.A.P.A. in dealing with positive pressures in a buildings drainage system.

The Studor P.A.P.A. (Positive Air Pressure Attenuator) is a revolutionary ‘world-first’ product developed to resolve the problems of positive pressures (transients / back-pressure) within the drainage systems of multi-storey and high rise developments.

This is the perfect complement to the existing range of Studor Air Admittance Valves (AAVs), providing a complete venting solution for any multi-storey building over 10 storeys high.

The below video feature helps explain the Studor P.A.P.A. in more of a visual format, and further product information can be retrieved here on the Studor P.A.P.A. product page.

Studor® P.A.P.A.™ from Studor on Vimeo.

Testing and Intellectual Rights

This revolutionary product was first tested in the laboratory of Heriot-Watt University in Edinburgh and was invented by Professor John A. Swaffield and Dr David Campbell. The invention of such a system remains unique in the drainage and plumbing field and is patented along with the designs of numerous other Studor products.

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Below Flood Level

As most people are aware, the flood level of a fixture (such as a wash basin) is the level at which water will begin to overflow – this could be various reasons, including a blockage in the pipe, or quite simply due to the tap having been left turned on with the plug in.

Air Admittance Valves (AAVs) are used in place of traditional secondary ventilation, not only providing savings in materials and installation time, but also superior drainage ventilation – ensuring that trap seals are fully protected, resulting in keeping bad odours within the drainage system and eliminating gurgling. The installation position of the AAV in relation to the flood level is critical.

As illustrated in the below video link, where low quality AAVs (‘B’ rated in accordance with EN12380) are used these have to be installed ABOVE the flood level of the fixture. This is because they are not able to withhold the pressure of rising water due to a blockage and they effectively become the location of the flood level. This means that additional, and commonly unsightly, pipework needs to be installed to be able to reposition the AAV above the flood level of the fixture, and thereby prevent the risk of water from flooding into the living space through the AAV.

Fitting an AAV ‘Below Flood Level’ from Studor on Vimeo.

By contrast, the Studor AAVs (which are ‘A’ rated in accordance with EN12380) are manufactured to high standards which ensure that they may be installed BELOW the flood level of the fixture up to 1 metre below, as they will not leak and will withhold the pressure of risking water due to a blockage – they are tested to 10,000 Pa.

An ‘A’ rated AAV is a solution for any single fixture, or a group of fixtures, connected to a single branch, i.e. branch ventilation in residential/domestic and commercial applications or stack.

An ‘A’ rated AAV eliminates unsightly pipework in a bathroom, for example by allowing the stack to be terminated low down, which means that it’s not obstructing the living space and the aesthetics are improved.

The European Standard EN12380 was introduced in 2002 to establish requirements, test methods and evaluation of conformity for AAVs. Setting the industry benchmark for quality and fitness for purpose, a key aspect of the standard is Table 1, which details the rating system in relation to operating temperature range and installation position in relation to the flood level of the fixtures:

Below Flood Level

The ‘A’ rating ensures that, should a blockage occur within a building’s branch or stack Sink in Bathroompipework, the AAVs below the flood level of the fixture will function correctly. It is imperative to know that, for the lifetime of the product, the AAV will operate and there will be no compromise in performance – the last thing you want to be doing is greasing the AAV’s membrane, as advised by some manufacturers, for example, because the seal has become dysfunctional after 5 years – thereby exposing the fixtures and living space to potential flooding.

All Studor products are designed and manufactured to be maintenance free, which means they are an incredibly durable, sealed unit which will last for the lifetime of the system onto which they are installed.

A Guarantee of Quality

Marked on each Studor AAV you will see the ‘A’ rating in accordance with the EN12380 standard, which provides reassurance of quality and performance. In some markets it is rare to see an ‘A’ rating on an AAV product, as not all manufacturers are prepared to guarantee longevity and ongoing performance.

By contrast, the Studor product range has been rigorously tested to and above many industry standards (including, amongst others, Australia, Europe, UK and the USA). Our finely engineered membranes have been tested to open and close thousands of times, and across a diverse temperature range.

Quality

Our confidence in our quality is supported by our unique lifetime warranty, which means that we will guarantee tightness and functionality of our AAVs for the lifetime of the system onto which they are installed – visit here for full details.

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State of the Nation

Nation Towers, Abu Dhabi, UAE, Specifies Sustainable SSPS.

To provide a sustainable solution, the Studor Single Pipe System (SSPS) was specified for installation at Nation Towers, Abu Dhabi, because it allowed for flexibility and simplicity in design, whilst also significantly reducing the amount of materials (pipework) required.

Nation Towers on the Abu Dhabi Corniche is a spectacular development comprising:

Air Admittance Valves, Drainage Venting Solutions

  • High-rise, residential apartments and penthouses
  • First class office spaces
  • A chic boutique-style mall
  • The deluxe St. Regis Hotel, incorporating the Nation Riviera private beach club.

A unique feature of the two towers is the Sky Bridge that connects both buildings, making it the world’s highest interconnecting bridge. Wherever possible, Nation Towers has been built with environmentally friendly, low emitting and regionally available products.

The SSPS was chosen because it provides superior drainage ventilation performance over other comparable conventional systems, which incorporate excess use of pipes. These substantial material savings reduce the quantity of pipe and the associated CO₂ emissions to produce and transport this pipe to site.

The P.A.P.A. - Studor. Drainage Ventilation Technology. Air Admittance Valves. Drainage Systems

The P.A.P.A. Part of the Studor Single Pipe System

Using SSPS products increased the sustainability of Nation Tower’s drainage ventilation without the need for roof or surface penetrations, thereby improving the thermal integrity of the building, whilst also making substantial savings in time, materials and labour costs. The Nation Towers project involved the installation of:

The SSPS design significantly reduced the quantity of pipe, compared to a conventional design, by over 36,000 metres. It also enabled the number of stacks to be dramatically reduced from 51 to 15 for Tower 1, and from 24 to 12 for Tower 2.

Due to the specialised Studor design, the velocity breakers and relief vents were also eliminated from the vertical stacks.

 

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The Only Line of Defence

Why the quality of AAVs must be high

The water trap seal is the only barrier between the drainage system and the living and/or Quality Air Admittance Valvesworking space; it is therefore essential that this is maintained at all times. The loss of a trap seal results in unwanted smells, noise and, importantly, the risk of pathogens spreading from the drainage system into the inhabited space. Whilst these are unpleasant in a domestic environment, there are serious health and safety concerns in a commercial environment, where the building owners and/or occupiers have a duty of care.

An Air Admittance Valve (AAV) is a thin but very effectual line of defence. It balances pressure in the drainage system, opening to allow fresh air in but sealing tight to keep nasties in their place.

Critical aspects of an AAV’s operation are:
• The need to respond quickly to changes in pressure, every time.
• The necessity to seal completely tight with no leakage whatsoever.
• Longevity of operation; as long as the drainage system itself.

Various standards exist across the world to “police” the performance and installation of AAVs. However, the implementation of these standards varies widely, with some countries having no relevant standards or approvals. Studor has been instrumental in working with various standards bodies, worldwide.

There is such a risk from the drainage system that there really should be standards in place to ensure that poor quality AAVs cannot be installed. With events such as the tragic SARS outbreak in the Amoy Gardens complex in Hong Kong, where it was proven that defective water trap seals had been a major contributor to the spread of disease, comes an increasing awareness and knowledge of the ever-increasing risks from drainage systems.

Quality Air Admittance ValvesUnfortunately, there are many poor quality AAVs produced around the world and a number of these have severely damaged the reputation of AAVs in many countries, often where standards did not exist, or false claims of compliance were made. All Studor AAVs are manufactured to the highest standards and because of our commitment to quality manufacture, all Studor products carry a “lifetime of system” warranty, which guarantees that all products will be defect free. It is our ethos to strive to exceed the statutory minimum requirements, not merely comply with them.

In Europe, EN12380 requires a “System 4” assessment of conformity, which means that no independent involvement is required to comply with the standard. However, unlike many other AAV manufacturers, rather than just relying on the CE mark, and the basic requirements to comply with this standard, and Studor has gone the extra mile to obtain KEYMARK approval.

 

The KEYMARK is a European quality mark and product certification scheme issued by Quality Air Admittance Valvesthe European Standard Organisation CEN (similar to the Kitemark issued in the UK by the BSI) and empowered by DIN CERTCO – the certification organisation of DIN, the German Institute for Standardisation. It proves that the Studor products fully comply with EN 12380:2002 through DIN CERTCO’s independent auditing and further reinforces the emphasis Studor places on quality.

In accordance with the KEYMARK regulations, Studor’s factories receive annual unannounced audits by NSF International and our products are tested by BRE, an independent testing institute, every two years.

Quality Air Admittance ValvesDuring the production process, every Studor valve is tested twice. In addition, a percentage from each production batch is randomly selected and submitted from the factories to our head office for additional in-house testing by our dedicated Product Engineer.

Studor products are developed not only to comply with international standards, but in many cases to exceed them. One example of this is in relation to the opening pressure of Studor AAVs. Each valve incorporates a Studor patented diaphragm. The quality of an AAV is determined by the material used for the diaphragm, as they need to be precisely engineered to prevent short-term failure. Very tight tolerances are required. Whilst EN12380 requires an opening pressure between 0 Pa and -150 Pa, the Studor AAVs open at -70 Pa, well within the specified limit.

A further example is in relation to the Maxi-Vent AAV. This is rated AI in accordance Quality Air Admittance Valveswith EN12380, which means that it can be installed below the flood level of the appliance to which it is connected and can be installed in extreme temperatures (from -20°C to +60°C). However, Studor guarantees that the Maxi-Vent will operate correctly, with no loss of function whatsoever, at a temperature of -40°C; ideal for areas such as Scandinavia, where the Maxi-Vent AAV can be installed in non-thermally insulated areas.

In the USA, standards ASSE1050 and ASSE1051 include high and low temperature endurance tests, which includes the valves being subjected to -40°F (-40°C) for eight hours before being returned to a laboratory controlled temperature of 73.4°F ± 3.6°F (23.0°C ± 2.0°C) and then being pressure tested. This is a material test, to ensure that the valves will continue to function if the material is exposed to low air temperatures. The same standards include endurance tests of 500,000 cycles in total, which is an aspect not considered within the European EN12380, as yet.

Quality Air Admittance ValvesBy contrast, the testing carried out to exceed the requirements of EN12380 is a functional test, with the testing being carried out whilst the valves are maintained at -40°C (-40°F), ensuring that the valves will operate correctly when they are installed in locations which may drop to this temperature. To the best of our knowledge, there is no one else in the market that is prepared to offer this extensive operating temperature range.

In addition to external installations, as the Maxi-Vent is often installed in roof spaces and voids where temperature can drop significantly (especially as the building insulation is often below the position of the Maxi-Vent), this adds to the product’s versatility. Even in climates where significant low temperatures are not an issue, the performance of the Maxi-Vent in exceeding this standard further confirms the quality of the product and the durability of the diaphragm. This guarantee is supported by an independent test report from BRE, which verifies that the Studor Maxi-Vent fully functions at -40°C.
For further information please refer to www.studor .net.

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Pathogen ‘Nasties’ and Protecting Your Water Barriers

The drainage system is often given little thought – we all know it’s there, but as long as we think it’s working it’s very much “out of sight, out of mind”.

In a domestic residence the drainage system transports waste from the bathroom, toilet and kitchen to the sewer pipes of the mains drainage or to a septic tank or similar. Water trap seals are used beneath the sinks (for example within a bottle trap) and within the U-bend of the toilet to maintain a water barrier between the drainage system and the living space.

Protecting Your Living Space From Pathogen Nasties
When the drainage is working properly the integrity of the water barrier is maintained all of the time, even when water is running or flushing through. However, when there’s a problem with the drainage (which could be for many reasons), the water barrier (the trap seal) can become depleted and the barrier is lost. This means that “nasties” within the drainage system can freely enter the living space – these range from unwelcome noxious gases through to extremely harmful pathogens.

Pathogen Types
A pathogen is a bacteria or virus which can spread disease, including the very well known ones such as Legionnaires’ disease, SARS and the hospital superbugs C. diff and MRSA.

The loss of a trap seal will commonly be indicated by symptoms such as bad smells and noises (gurgling, whooshing or the intake of air). If any of these are experienced we recommend the cause is looked into and rectified as quickly as possible – in most cases, quite simply the installation of one of the Studor AAVs or our combined trap and AAV will solve the problem.

Amoy Gardens Estate in Hong Kong
The tragic outbreak of SARS (Severe Acute Respiratory Syndrome) in the Amoy Gardens estate (Hong Kong) in 2003 provides extreme example highlighting the importance of maintaining water trap seals and preventing nasties from the drainage system entering the living space:

The first person of the outbreak developed SARS symptoms on 14 March 2003. When visiting his brother, who owned an apartment in Block E, at Amoy Gardens that same day he used the toilet whilst he was suffering from diarrhoea. SARS then spread throughout the Amoy Gardens estate at an alarming rate, resulting in 321 infected cases and 42 deaths, with the highest concentration of infections being in Block E.

Research has shown that many SARS patients excrete the virus which causes SARS in their stools. In light of the fact that many residents at Amoy Gardens had been complaining about bad smells for some time, and that many U-traps were found to be completely dry, it is believed that the virus spread through the drainage system and contaminated droplets entered the living space of other apartments, infecting their occupants.

In fact, the World Health Organisation’s Environmental Investigation into the outbreak states that defective water trap seals in the drainage system had been a major contributor to its spread.

As mentioned above, this is an extreme example, but it does illustrate why everything should be done to keep nasties in their place – the drainage system – and well away from the living space!

Further information is also available on this government document which summarises the main findings of the Amoy Gardens Estate Investigation.

 

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Don’t blow your top!

Guest blog by Dr. Michael Gormley
MSc MPhil PhD CEng MCIBSE MIET FHEA

Dr.Gormley is a specialist in water supply and drainage as well as an electrical building services engineer. Read his full biography here.

The tradition of venting building drainage systems through the roof is as old as modern systems have existed. Most modern appliances and techniques date back to Victorian times in Britain, around the middle of the 19th Century, when there was a flurry of research and development activity – partially fuelled by the industrial revolution, but also driven by the desire for safe sanitary conditions in the rapidly expanding towns and cities at the time. This process continues to this day, however this is now on a global scale, with the recent significant milestone that there are now more urban dwellers than rural dwellers in the whole world.

The Victorian obsession with cleanliness led the development of heavy water usage appliances, with toilets using as much as 40 litres per flush – with appropriately strong names such as the ‘Tornado’, the ‘Dreadnought’, ‘Trident’ and the ‘Deluge’. They really did believe in the old adage that ‘cleanliness was next to godliness’ and cleanliness meant lots of water and open roof vents on the drainage stack.

Some pretty cool facts and a history lesson to boot, but what has this got to do with modern venting techniques? Well, essentially the struggles of the early Victorian plumber and sanitary engineer are the same as their modern day counterparts. Providing safe and efficient sanitation solutions is as challenging now as it has ever been, more so in many cases, as water conservation requirements demand that modern systems do the same job with less water and materials.

While 19th Century researchers made great efforts to understand drainage systems and laid down the fundamental physics of air flow and the importance of friction, there were limitations to what they could do as they only had rudimentary systems with which to work. Some great figures emerged and among those writing on the subject was Osborne Reynolds – famous for his work on fluid mechanics (remember all those equations with Reynolds number from your fluid mechanics classes? That’s him). We truly are standing on the shoulders of giants in this field.

‘Every generation brings advances and ours is no exception – we have a few tricks up our sleeve too.’

Modern mathematical and computer based modelling techniques have allowed us to charge ahead with advances at a rate hitherto unthinkable. This step change has seen The P.A.P.A. - Studora return to look at the fundamental physics of what is going on in there, under the sink, behind the toilet and in your loft. To blow my own trumpet here a bit, and to shout on my own team – central to this new ‘industrial revolution’ of sorts has been the work from Heriot-Watt University, initiated by the late John Swaffield – co-inventor of the P.A.P.A.TM – John’s work on numerical modelling embedded in the computer program AIRNET has allowed any system of any size to be modelled and venting arrangements assessed before the contractor has laid the foundation stone. John’s work is continued by myself, together with colleagues, Lynne Jack, David Campbell and David Kelly.

So, again, where are we going with this?

Well, most of the innovations of the past 20 years have come out of this fundamental research – the P.A.P.A.TM and the DYTEQTA-SYTSTEM to name a just a few – to this list I would like to add ‘Sealed drainage systems’. This innovation was first used in the O2 Dome in London when it was being upgraded to an entertainment arena in the mid 2000s. As a direct result of the developer’s request that the system should not penetrate the iconic tent-like roof structure.

So, with a brief which precluded the use of roof penetrations, in a building with high peak usage capacities the challenge was immense. The sewerage infrastructure wasn’t straight forward either as part of the system was below the river level, so pumping stations were required.

The methodology used to ‘seal’ the above ground drainage system would not be possible without active control of pressure transients. Active control is a method of dealing with pressure transients as close to their source as possible. This is the ideal goal – trying to draw air in to a system through a high friction, small diameter pipe, simply means that the transient will have sucked out the nearest water trap seal long before the air has arrived from the top of the building. In the case of positive transients a similar problem exists in that the protection afforded by parallel vent pipes is negligible and wholly determined by the ratio of cross sectional areas of the stack pipe and the vent pipe. So, traditional venting doesn’t always achieve the goals set out on the design table.

Actively controlling pressure surges is a much more effective way to protect water trap seals.

Air Admittance Valves (AAVs) provide the correct quantity of air to mitigate against negative pressure transients – and this quantity varies automatically with the magnitude of the applied negative pressure transient. In the same vein, positive pressure reduction devices, such as the P.A.P.A.TM (Positive Air Pressure Attenuator) provide an alternative route for positive pressure transients, protecting water trap seals by attenuating the pressure wave in terms of its magnitude and it’s wave speed, slowly releasing the air back into the system in a non-destructive way to ready itself for the next positive pressure event. Taken together, AAVs and the P.A.P.A.TM operate to maintain system pressures at acceptable levels, thereby ‘tuning’ the system to desired pressure levels.

But what if the top of the stack is sealed, will the whole system not pressurise?

The simple answer to this question is no.

The building drainage system is a dynamic multi-phase fluid and solid carrying system. Air currents circulate between stacks, into sewers and around loops. As long as air is provided by AAVs to counteract the negative pressure transients and positive surges can be dealt with by the P.A.P.A.TM then the system cannot pressurise.

The design of the O2 Arena drainage system wouldn’t have been possible without the use of numerical modelling with AIRNET. Simulations of every possible event scenario took several months to complete and produced graphical output running into the thousands. The result was a clean bill of health for the active control solution in the sealed building. By simulating extreme events it was possible to predict how the system would cope, what pressures would be expected and what the limitations were.

So, from Victorian toilets to a state of the art arena in 21st Century London we can see that without innovation we cannot achieve the necessary goals of improved sanitation for all, in any global context. The combination of academic and industrial research; new technologies, techniques and design methodologies, combined with renewed confidence in our own ability to move things forward in this generation, means that we can cope with existing problems, and, more importantly, whatever challenges are thrown at us in the future.

November  2013.

Dr. Michael Gormley
MSc MPhil PhD CEng MCIBSE MIET FHEA
Institute for Building and Urban Design
Senior Lecturer in Architectural Engineering
Room 3.40 William Arrol Building, School of the Built Environment
Heriot-Watt University, Edinburgh, EH14 4AS
e: m.gormley@hw.ac.uk  t: + 44 (0) 131 451 8262

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