Pushing the Boundaries

Pushing the Boundaries

The opportunity to develop alternative solutions allowed Sellick Consultants to collaborate with world leading academics to deliver the first alternative solution under the National Construction Code in the nation’s capital.

The Plumbing Code of Australia (NCC Volume 3) now provides hydraulic consultants and plumbers with the opportunity to deliver a performance based outcome to projects in a similar manner to which Fire Engineering outcomes are applied to projects.

There are often design situations which standards or other referenced documents may not have envisaged. Alternatively, a practitioner may see a new or innovative way of designing a plumbing or drainage solution that provides important benefits. If the practitioner wants to use an alternative approach, they have the opportunity to do so – on the understanding that their proposal must achieve the Performance Requirements of the PCA. This is referred to as the ‘Alternative Solutions’ approach.

Sellick Consultants recently prepared a performance based alternative solution for a significant project in Canberra, Australia – Manhattan on the Park.

The project consisted of 330 residential apartments in Canberra city with associated car parking and tenant facilities such as a gym, swimming pool, BBQs and the like. Sellick Consultants was engaged by the Developer for Civil Engineering and Hydraulic Services Engineering Consultancies.

“Relevant standards had not kept up with water conservation implementation so we used the provision in the NCC Volume 3 to undertake a performance outcome for sizing of drainage on the Manhattan project,” national director  hydraulic services Sellick Consultants Brad Williams says.

“The client wanted to demonstrate that water conservation implemented as a mandatory requirement by council did not necessitate amplification of existing offsite sewer network, and the existing network was adequate to cater for reduced flows due to water conserving fixtures and fittings.”

Sellick Consultants, with the support of academics from Heriot Watt University (HWU), Edinburgh Scotland, that the use of low flow fixtures, tapware and appliances could support a reduction of the sanitary drainage and therefore avoid an upgrade of offsite infrastructure at an estimated additional cost to the developer of $500,000.

Given this was the first alternative solution to be put forward in the ACT, the local authorities were vigilant. They wanted to ensure that all steps were being undertaken to prove that the reduction in pipe size would have no detrimental effect on the future operation of the sanitary drainage network within the building.

Sellick Consultants had to prepare a formal engineering brief outlining variances from the deemed to satisfy Australian Standards and had to brief all stakeholders on the proposals put forward on the project for formal acceptance.

“Initial reluctance by the local Authorities to support our performance based outcome led to the engagement of HWU, who are acknowledged as a world leader in drainage research,” Brad explains.

“They were keen to be involved in a “live” project and understood the basic matter at hand – water conservation impacting on the carrying capacity of drainage. HWU developed flow and time profiles for all fixtures and fittings and loaded this information into their Drain Net software simulation model developed specifically for the project.

HWU used statistical/probability numerical simulation over a three hour window of 0600 to 0900, where every fixture and fitting in all of the apartments was used, deriving a maximum flow rate in the drainage network adequate for the installation of a 150mm diameter drain rather than a 225mm diameter drain as prescribed by the relevant Australian Standards.

As you can imagine, the fixture and fitting manufacturer would also have to back up their products’ claims and have the ability to prove that their products could stand up to the kind of treatment being asked of the alternative solution.

“The local authorities required a written warranty from Studor to state that the performance based outcome would have no detrimental effect on their air admittance valves and positive air pressure attenuators installed within the sanitary plumbing system and that Studor were willing to warrant their products within this project. Mr Steven White from Studor was also consulted and was a key stakeholder. He had no hesitation in providing the warranties given that HWU were involved in the verification of the outcome,” Brad says.

Sellick Consultants informed ABCB of its proposal to which they advised Sellick that the matter was something the local regulator had to consider but they would be interested in understanding our proposal and the outcome. It is important to remember that the ABCB is merely a facilitator and not the regulator.

“We did pass on our final engineering brief to them for their information and this included the paper prepared by HWU to validate our claims.”

Sellick Consultants has been granted an Australian Innovation Patent by the Australian patent office. The patent takes into account the impact of WELS ratings of fixtures and fittings and adjusts drainage/water loadings accordingly to suit the water conservation measures adopted into the project. This is particularly important locally because in the ACT a 40% potable water reduction measure is mandatory and water conserving fixtures are essential to meet these targets.

“The IP adopted assists to adjust pipe sizing to suit reduced flows apparent in both drainage and water pipes due to water conservation in buildings. On larger, more complex projects, further analysis can be undertaken using statistical probability and numerical simulation using the time and flow patterns as was done on the Manhattan project.

“The IP is currently being accepted on local ACT projects by the Private Plumbing Plan Certifiers given it stemmed from the R&D that was undertaken on the Manhattan on the Park development.”


News of such innovation and thinking spreads across the industry like wildfire and switched on suppliers begin to ask questions.

“Sellick Consultants have been approached by suppliers such as Geberit to identify how the IP can assist with pipe size reduction on high rise residential apartments for their Sovent system and we also work closely with Studor who are also aware of impact of water conserving fixtures/fittings on drainage design.

“Despite engaging one of the world’s leading drainage research teams, our local regulator was still concerned that the system would fail under an extraordinary condition. To that extent they asked us to investigate the impact of a two minute window at halftime of a State of Origin game, where every WC was flushed in all 330 apartments.”

Sellick duly inputted this outcome into its engineering brief, which indicated that the 150mm pipe size was adequate; however, since the completion of the building it has been using Switch Automation to remotely monitor potable water consumption to the entire building, logged every 60 minutes.

“We were pleased to review the data output following State of Origin games over the past three years and found that there was no marked increase in water consumption.

“The ability to monitor water consumption has indicated that in practice the amount consumed is approximately half of the theory put forward by HWU – possibly because they used every fixture in every apartment over a three hour window whereas in reality this is rarely the case,” Brad says.

“In fact the information we are garnishing indicates that within the apartments water consumption peaks on a late Sunday morning when most tenants are home doing their weekly chores. It still doesn’t come anywhere near the HWU statistical analysis. This begs the question whether there is still room for improvement in the design of plumbing and drainage systems using data derived from active buildings with smart metering into the future.”

No doubt more research, innovation and technology will spur more opportunities to answer that and many more questions in the future. Just as more plumbers and consultants will develop alternative solutions that benefit the industry as a whole.

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