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Reduced flush volume and drainline testing 16 February 2009
Tags: Sanitary Equipment, Toilets, Pipes & Fittings, Toilet Testing / Performance, Drainage & Venting, Dry drains, Laboratories, Climate Change / Sustainability, Codes, Standards & Regulation, Innovation, Research & Knowledge, Water Efficiency / Dry Drains, Australasia Page 1 of 3 | Single page
Does reduced flush volume have a negative effect on the performance in the drain line? One manufacturer was keen to find out.

The increasing practice of reducing the volume of water used to flush sanitary fixtures is raising some drain line performance questions across the plumbing world, and for good reason.

While fixture manufacturers focus on the performance of their products in the laboratory, we can’t ignore what effect these new technologies are having on the overall performance of the plumbing system.

Reduced-flow, single-flush toilets began to appear in Europe in the 1970s, particularly in the Scandinavian region with products from Gustavsberg and Ifo.

Then, and even to this day, water authorities around the globe raised concern about lowering the volume of flush water, when they didn’t know the effect such a reduction in quantity would have upon the flow within the associated drain lines.

Australia is the second-driest inhabited continent on earth and has major issues with maintaining adequate supplies of potable water in both city and country regions. Thus water conservation is considered very important for the nation’s growing cities with their reliance on unsustainable water supplies.

In 2007, Australia has even more significant issues with its dwindling water supply due to the prolonged effect of a severe one-in-one-hundred-year drought affecting many parts of the country.

Australian sanitary manufacturer Caroma is the dominant supplier of sanitary fixtures to the Australian and New Zealand markets, which have a combined population of 25 million. In 1993 the company launched the first 6/3 dual-flush toilet, using just 6L (1.6 US gallons) for full flush and 3L (0.8 US gallons) for half-flush. This was the first instance when the technologies of both reduced-flush and variable-flush volumes were integrated.

Manager of Caroma’s research and design department, Dr Stephen Cummings a leader in his field, has long held the view that while the involved and exacting process of designing and manufacturing toilet suites is of paramount importance, a critical issue is that the suite must be considered part of a ‘balanced plumbing installation’.

“Much of the critical design and production process is based upon the need to retain as much of the energy of the flushing water for as long as possible within the pipeline system. This flow transportation performance can be easily impeded if the drainlines taking the waste discharge from the toilet bowl are incorrectly or poorly installed.

“The construction of pipe-work with correct workmanship, gradient, true bore, smooth jointing and quality materials are all essential factors that will significantly affect the overall performance,” Dr Cummings says.

Dr Cummings initiated the design and construction of a pipeline test rig at the corporation’s Sydney manufacturing centre several years ago. The elevated test platform, situated approximately 4m (12 feet) above ground level, allows toilet suites of various designs to be easily connected to 100mm (3.9 inches) and 80mm (3.1 inches) diameter drain lines. These clear plastic drain lines, that extend for some 60m (200 feet) and form the longest test installation of its kind in the world, enable the test team to easily observe the waste flow performance from up to five of WCs set up on the rig using varying drain line grades configurations and low-flush discharges.

A number of intensive test programs were carried out over several years incorporating national and international Standards and procedures where applicable. The research program provided valuable information regarding the flow and behaviour of waste through the toilet bowl and the drain line when using various low-flush discharge volumes.

By using various low-flush volumes, combined with the introduction of synthetic solids and toilet paper, the researchers gained valuable information and a better understanding of the performance criteria required to achieve a ‘balanced plumbing installation’.

Test rig supports and pipeline hangers have been designed and installed to replicate conditions experienced in the field. Gradients were accurately achieved initially by the use of a dumpy level, which proved to be very successful in achieving a continuous and correct gradient.

More recently, the researchers have utilized current electronic levelling devices to obtain an easier and even more accurate process of levelling. While adjustment is labour-intensive, the rig will allow a variety of tests to be carried out at a number of gradients, and differing pipeline sizes and fitting conditions can also be tested.

In 2004 Caroma again set a new low benchmark for the industry when it introduced the first 4.5L/3L (1.2/0.8 US gallons) dual-flush toilet system.

However, simply reducing the volume of water entering a cistern bowl can lead to issues and many researchers, suppliers and water authorities have invested time and resources in undertaking reviews.

The real science behind producing a reduced-flush performance toilet is in matching the flow of water from the cistern to the precisely designed configuration of the toilet bowl. In one action the flow from the cistern into the bowl needs to remove solids and paper as well as cleanse the bowl, but even then using ultra-low-flush volumes the task is not complete.

The characteristics of the head of water exiting the trap and flowing down the drain line is critical to the long-term performance of the complete plumbing system.

As Dr Cummings explains: “the key requirement between the WC and drain line is to fully discharge the waste from the bowl outlet using intial part of the flush and then to achieve steady flow conditions within a minimum distance within the drain line system in order for the waste to effectively clear the drain line.

A significant amount of development work has been involved in performance matching the bowl and sump configuration with the reduced flush volume discharged from the cistern. Importantly, the performance observed on the testing rig was validated in trials in the field with existing drain line installations.

Most Australians live in single-level housing, characterised by long-run drain lines. In single-level housing the performance of such drain lines is critical, whereas in multi-storey apartment blocks plumbing stacks are far more forgiving.

Caroma’s 4.5/3L SmartFlush™ technology was launched onto the market after an extensive field trial program was conducted in Melbourne in conjunction with Yarra Valley Water and other major water authorities in Australia.

The program included retrofitting 100 SmartFlush toilet suites into private homes that had previously been fitted with toilets of varying higher-flushing volumes. A number of locations were included of ‘above average’ difficulty, in terms of the length of the minimum grade line, varying grades along the line, old earthenware pipes, and toilets isolated from any assistance from upstream fixtures.

According to John Park of the Plumbing Industry Commission (PIC), 10 sites, with a range of drain materials from old earthenware to PVC, were selected for inspection by CCTV. “No blockages occurred during the trial, and to the best of our knowledge there have been no blockages since,” he says.

The PIC protects consumers’ health and safety by administering the licensing and registration system for plumbing practitioners, and promoting and enforcing plumbing standards in Victoria.

In addition to research into technical performance, Caroma also surveyed the homeowners, who confirmed their satisfaction with the performance of the new toilets, including bowl cleaning and removal of waste. The SmartFlush product was then unconditionally released to the market with the support of water companies and regulators nationally.