Pressure Attenuators – seven years on
The uptake of the Pressure Attenuator – an alternative to relief venting – was quite rapid considering the shift required in traditional thinking.
The first project that utilised them was the Chevron Apartments in Melbourne. The ink was barely dry on Amendment 1 to AS/NZS 3500.2.2003 when CLG Plumbing applied Pressure Attenuators to this project. Due to the constantly changing floorplan, a standard relief vent chasing the stack would have been impractical. The placement of one PAPA (Pressure Air Pressure Attenuator) at the base of each stack greatly simplified the design. From this, the application of the system has spread throughout Australia on a constant basis.
Although Melbourne has the greatest number of these projects per square metre, there are now PAPA projects in every State. Even as far afield as Darwin, the 29 floor Mantra Pandanas hotel/apartment tower streamlined their drainage system with the application of this system.
Utilising research of the School of the Built Environment at Heriot-Watt University (HWU) in Edinburgh, Scotland, it was discovered that all drainage systems used around the world had a fundamental problem with the positive pressure resulting from the discharge of waste down a multi-storey stack. The PAPA was designed to deal with this. Rather than obstruct the flow at every floor, the discharge continues freely down the stack.
A complete Studor System incorporates Air Admittance Valves (AAVs) on all the branch line fixtures, which open as the discharge passes (regardless of fixture usage), thus allowing air into the system. When the discharge reaches an offset or base of a stack the liquid component of the discharge falls across the full diameter of the stack pipe causing a ‘water curtain’. This then creates a barrier, stopping the air following behind and causing a positive pressure wave that rebounds back up the stack causing movement or, at worst, loss of trap seals.
HWU research proved a number of points:
1. The discharge reaches terminal velocity over a minimum of three floors.
2. A pipe of at least the same diameter or larger is required to provide an effective receptacle to the positive pressure wave. A pipe of lesser diameter simply takes in a proportion of the wave, allowing the major proportion to carry on up the stack.
3. The rate of change is also a major contributor to trap seal depletion.
Besides being a suitable receptacle for the pressure wave, the PAPA also slows it down (attenuates it) from 320 metres per second to 12 metres per second. In addition, a key feature of the PAPA, is that it has no moving parts, being comprised simply of an ultra-responsive bladder contained within an outer casing. The whole unit connects to the stack via a proven ‘key seal’, which has been used on the Studor Maxi-Vent for over 30 years.
Despite recent comments to the contrary, the Studor PAPA requires no maintenance – quite simply ‘fit and forget’. A fundamental part of the drainage system, it is designed and engineered to last the life of the plumbing system. To create a device for this function requiring regular servicing would have been self-defeating, as no-one could guarantee this would be carried out throughout the full life of the building. In fact, Studor states that if the PAPA is correctly installed in conjunction with their AAVs on the branch lines and fixtures, that they will warrant the correct ventilation function of the entire drainage system for the lifetime of the plumbing system installed in the building. For this reason, in many States and countries access is not even required.
With the reduction in pipe to that required quite simply to transport the waste, the Studor System is a big plus for the environment, as well as providing freedom of design and ease of installation.
Consequently, the Studor System has become a success story throughout Australia. Some of the most spectacular projects have been realised utilising the simplicity of this drainage ventilation system, including the Hamilton Harbour Apartments project in Brisbane, the SA Water Building (VS1) in Adelaide, Fairfax’s Media House and the South Wharf Hilton in Melbourne, BHP’s City Square tower in Perth, the Sydney Tower and even the Wellington Centre in Hobart.