Downstream plumbing does not attract much interest until something goes wrong. Now with the emphasis on water conservation there are concerns that lower building drainage flows will mean future problems.

The most common plumbing system design in the developed world is based on the hydraulic performance of gravity – a system fundamentally unchanged since the 19th century.

However, as global water and plumbing industries are discovering, there is clear evidence that the system is showing signs of stress due to significant reductions in drainage flow.

Global warming concerns and water shortages create problems of their own.

These problems are compounded by government water-saving strategies, together with more recent moves to reduce plumbing costs, such as reducing the venting requirements and changing the design of drainage connections.

In Australia, lower drainage flows have been brought about by reducing water use to counter the effects of enduring drought. Such reductions also compensate for a lack of investment in water infrastructure to meet the demands of growing cities.

The focus has remained on reducing the performance of various fixtures (toilets, faucets, showers, etc), with insufficient consideration given to the effect on the overall system.

A salient example of the importance of matched plumbing design is the Hong Kong SARS pandemic, which brought about big design changes in plumbing.

The 2003 report by the World Health Organization (WHO) found inadequate plumbing to be the most likely contributor to the spread of SARS in residential buildings – as well as several other infectious diseases around the world.

The push to improve the water efficiency of household appliances and plumbing fixtures has brought about substantial reductions in water use in most Australian cities, attracting the interest of many other countries.

Australia is committed to even greater water savings for toilets, faucets and other point-of-use fixtures. However, a study is urgently required to investigate the influence of toilet flush volumes of less than 4.5/3L (1.2/0.8 gallons) on existing drainline systems complying with the AS/NZS 3500 Standard.

The growing uptake of graywater and blackwater recycling systems has further affected drain lines by compromising engineered drainage systems in dwellings and commercial buildings.

Some Australian States have proposed amending building codes to allow for separate graywater and blackwater drainage systems in dwellings, a notion that has rung some alarm bells.

In Australia, New Zealand and many other countries there is little evidence of adequate research and testing to confirm the long-term effect of such changes.

In the latter half of 2007, the Australian and New Zealand Plumbing Regulators Forum (NPRF) met to consider the issue, and agreed to develop a study program for which funding would be obtained.

The project – Australasian Scientific Review of Reduction of Flows on Plumbing and Drainage Systems (ASFlow) – is in the process of finalizing the briefing paper.

NPRF technical advisory committee chairman Jeffrey Clark, who represents the South Australian Water Corporation, believes that some intervention is justified.

“We are concerned that if flushing volumes for toilets are further reduced, there could be implications for our internal plumbing systems as well as external infrastructure. This would affect the way Australian Standards are written – they would need to be substantially changed.”

Clark doesn’t think we have gone too far in our attempts to save water but he believes trials are justified to ascertain to what extent the reduction adversely affects plumbing.

“In South Australia we’ve had issues with commercial plumbing systems causing blockages. We’ve also had issues with waterless urinals and other such systems. We have made some changes in the current amendments to AS/NZS 3500 to better protect the drainage system.”

The main problem with urinals that do not use water is the build-up of uric acid, which blocks the urinal trap and drain pipe.

Roger van Gelder, an independent water conservation consultant, has done some investigation on no-water urinals at the University of Washington (N.W. USA) and found that a ‘sludge’ builds up in both the horizontal and vertical legs of the drain pipe behind the urinal.

At the time of printing the sludge had yet to be analyzed to determine exactly what it contains but van Gelder believed it to contain hair, proprietary fluid from the trap, bacterial growth, urine crystals, etc.

Industry experts John Koeller and Bill Gauley witnessed the research and reported that apart from the sludge being “pretty disgusting!”, the drain pipes were between 1/3 and 2/3 blocked after six months (new drain pipes were originally installed).”

Clark says the industry, in conjunction with the NPRF technical advisory committee, has been conducting long-term trials in the performance of waterless urinals.

“Without water flushing the drain, the discharge pipe waste line will eventually block up. So we need to review the Standards to address the need for better overall design consideration. This could mean running fixtures past the urinal first, instead of having them on dead legs or dead branches.”

Some of the long-term effects of problem drains are being experienced, with home-owners calling plumbers out to rectify drainage system blockages that cause odors inside buildings.

Plumbing regulators are dedicated to conserving water. However, Clark and other regulators also want to ensure that plumbing systems are not causing blockages that can lead to overflows and adversely affect public health and the environment.

Trials are taking place in Perth, Western Australia, and Canberra, the national capital. The continuation of such trials is essential to the overall outcome of the project.

Caroma, Australia’s main supplier of plumbing fixtures, “fully supports the project because it believes that fixtures should be fully compatible with the drain line i.e. fully matched in performance.”

The technical advisory committee aims to have all trials completed in the next 18 months.

Caroma’s research and design manager Dr Steve Cummings has been researching other overseas models to compare overseas practices with Australian practices. He found that other countries were facing similar problems.

Germany in particular has reduced its flow rates and water consumption to almost half the level of a typical Australian dwelling.

There is concern among the general community in the United Kingdom regarding government water containment initiatives.

Waterwise UK head of research Joanne Zygmunt says sewers in many places have to be flushed with substantial amounts of water because flows from dwellings are insufficient.

“The average per capita consumption of water in the UK is about 150L (40 gallons) a day. If this goes down to as low as 100L (26 gallons), problems may be experienced. The government vision for new homes is about 110L (29 gallons) per person per day.”

Question: are the sewers in the UK typically combined (i.e. is the same sewer used for sanitary as well as storm water)? Based on the following few sentences, should you say, “In the past the UK could rely on the generally dependable rainfall to allay any such concerns.”

However, Waterwise director Jacob Tomkins concedes that water scarcity is a real concern.

“In reality the UK has less available water per person than most other European countries, and the Thames Valley is technically classified as semi-arid,” he says.

“Climate change is making this worse as rainfall becomes less regular and more intense, leading to floods and droughts. At the same time the UK is experiencing a population shift to the driest parts of the country, and households are smaller but with higher consumption.”

In the past two years southern England has had the worst droughts and the worst floods for a century, both of which resulted in water shortages.

“This is not just a southern England problem – there was a drought in Dundee in north-east Scotland a couple of years ago.

“The Government is responding to these issues by developing new legislation to promote water-efficient housing and bathroom fittings, with the aim of reducing per capita consumption from 150L (40 gallons) to 120L (32 gallons) per day.”

Tomkins also says low-flow studies have been inconclusive.

“There is some concern that reduced flow will result in sewer blockages.

However, it generally seems that the problem stems from poor sewer design and maintenance, and the flushing of non-sewerage items.”

The UK Environment Agency is due to release a report titled Less Water to Waste: The Effects of Water Efficiency on Wastewater Flows. It is hoped it will shed light on water conservation methods and their effect on infrastructure.

Yet it is clear that the UK is still lagging behind Australia. The NPRF findings should provide a telling prognosis and allow the Australian plumbing industry to more effectively combat water shortages (and global warming in the longer term) and curb any initiatives that are being taken too far.

It may be possible to take a leaf out of Veritec Consulting principal Bill Gauley’s book. Since 2003, Gauley has been conducting tests in North America on flush performance, known as MaP testing (maximum performance of toilet fixtures).

In the US and Canada it seems that the 6L systems are more than sufficient. In 2006 WPR spoke to Gauley, who uses soybean paste (with similar properties to human waste) to test the efficiency of certain toilet models and their capacity to flush.

“Based on the results of extensive performance testing, manufacturers stepped up to the plate and began making far better toilets,” he says.

“While the minimum threshold for providing customer performance satisfaction is set at 250g (0.6lbs), some models today can flush over 1,000g (2.2lbs) and be classified as truly exceptional.”

Tests by Gauley are ongoing – and required – as North America moves towards blanket manufacture of ‘ (actually HETs have “effective’” flush volumes of 4.8L (or 1.28G). As drought hits harder and initiatives to curtail water use become more prevalent, MaP testing takes on greater importance.

Gauley has also completed a series of tests to determine just how far low flush volume toilets can transport waste through the drain pipe. His research has found that while toilet flush rate is an important factor, flush volume is by far the most important aspect concerning drainline carry distance.

Gauley says, “If we intend to use toilets flushing with less than about three litres of water in our homes we may have to redesign our drainage systems, e.g., steeper slopes, smaller diameter piping, and perhaps less intrusive couplings”.

He strongly agrees that more research must be done to assess the effects of lower flow rates in our drain systems.

“One outcome may be,” he says, “that we allow lower flush volumes for residential installations where supplemental flows from showers, baths, and clothes washers help transport waste to the sewer and higher flush volumes for commercial installations where drain pipes have larger diameters, flatter slopes, and little or no supplemental flows.”

Australia is well ahead of North America in its plans to conserve water: WELS Standards are compulsory, whereas Uniform North American Requirements (UNAR) is a voluntary program.

Yet, we should take heed of Gauley’s tests and monitor them closely as the capacity of toilet systems in North America continues to be reduced.

The possibility of blockages, pungent odours and drain damage doesn’t bode well for future water reductions, yet the results of test trials are still at least 18 months away and it would be prudent of any agency thinking about reductions to rethink its stance until all the evidence is in.

WPR will update this important issue as progress is made. In the meantime, if you believe any of your experiences in this area are worthy of sharing with the global plumbing community, please contact us at: info@wpr.com.au