Water efficiency is an important measure in green building everywhere, but in Australia — one of the driest countries in the world — water conservation is more widely practiced and water awareness is generally higher than it is in North America.  In addition to pioneering water efficiency, Australians have discovered some problems due to the use of efficient, low-flow fixtures.  One is the potential problem of "dry drains," however, a new invention called the Drainwave aims to solve the problem. 

"Dry drains" is the term given for plumbing problems arising from the use of newer, more water efficient fixtures and facilities. Plumbing pipes have generally been designed and installed to transport solids with a flow of water. As low-flow fixtures have become more common, problems with plumbing systems have sometimes arisen.

Australian construction reporter Hartley Henderson noted in an article for Facilities Management, "Continual reductions of water flows in the plumbing systems of buildings, however, can result in ‘dry drains,' whereby flows may be insufficient to effectively flush toilet discharges through the piping system. The situation is further compounded with a trend to extract greywater from plumbing systems for reuse."  

Enter, the Drainwave

The Drainwave was featured on the Australian television show "The New Inventors," where it won a People's Choice award. The Drainwave is simply an inline accumulator that collects blackwater (sewage and wastes) and greywater (from sink drains) and discharges it through the sewer only when there is enough of a volume to propel the waste as needed.

According to the Drainwave website, "Using two inlet ports, the Drainwave collects greywater from general household use (sink, shower, washing machine, etc) and combines this outside the house with black water from the toilet. The combined waste water leaves the Drainwave and surges through the pipe network to the main sewer line to minimize blockages.

Once 9.5 liters (2.5 gallons) have accumulated in the Drainwave, it automatically empties itself with enough volume to keep drain pipes from becoming blocked.

The Drainwave accomplishes its goal without use of additional water, which preserves the efficiency of low flow fixtures and other measures, while also allowing existing piping and infrastructure to continue to function as it was initially designed and built.  It's not a pretty thing, it's something meant to be hidden out of sight.  But it has the potential to avert a lot of unpleasant problems, particularly for water efficient buildings.

With the increasing adoption of LEED in green building, and the now mandatory water use reduction called for under LEED 2009 (and points available for water use reduction targets of 40% better than baseline), water efficiency is becoming more commonplace in the US. Similarly, European standards are also including water use efficiency as part of green building programs.

The Drainwave can be installed underground outside the house, making it possible to use in retrofit installations, or can be installed in uninhabited parts of the house.  Although this device is aimed at the residential market, versions to serve the commercial market can easily be anticipated.

[+] Video on the Drainwave website.