MEDIA RELEASE
Keeping Sewerage Separate
10 August 2006
There can be few sights more distressing for a property occupier, than seeing raw sewerage discharge into the open.
The risk of sewerage overflows after heavy rain highlights the importance of keeping storm water systems and sewerage
systems completely separate.
"Basically, whatever goes down the drain from within a building, goes into the sewerage system, and is piped to a
sewerage treatment centre" according to BRANZ Science Communications Manager, Chris Kane. "Sewerage systems are
constructed to collect laundry, kitchen, bathroom and toilet wastewater."
The same is true for buildings with a septic tank system. In this case, all household wastewater is held in an
underground septic tank, allowing microbial action to break down solid toilet waste. Over time, the septic tank fills up
and the liquid run-off is diverted to a soak pit, while the semi-treated solid waste settles to the bottom of the tank.
It is recommended that tanks are pumped out every two to three years.
Storm water drainage systems are designed to cope with rapid, heavy loads, although in extreme weather conditions,
flooding can occur.
Diverting storm water into either a sewerage system or a sceptic tank would create serious risks of overflow and
uncontrolled discharge of untreated waste. It is a legal as well as a public health requirement to keep both systems
separate.
BRANZ has numerous publications available on plumbing and drainage systems, and regularly runs training courses for
building professionals who want to learn more.
BRANZ & Building Research - Who We Are
BRANZ Ltd delivers research, testing, consultancy and educational services. While BRANZ Ltd has its own Board, it is
owned by Building Research but draws only 40% of its income from investments by Building Research.
BRANZ should not be referred to as the Building Research Association of New Zealand, even by way of explanation. BRANZ
Chief Executive is Peter Robertson.
www.branz.co.nz
Building Research is a separate entity governed by a Board drawn widely from industry. Building Research invests in an
extensive range of research, technology transfer and scholarship activities, with funds provided by the Building
Research Levy.
www.buildingresearch.org.nz
Homeowners can call BRANZ on 0900 5 90 90 for practical building information. Calls cost $1.99/min +GST.
Building Industry Professionals can call 0800 80 80 85 to speak to a technical advisor.
ENDS