Keep Stormwater & Wastewater Pipes Separate

17 June 2014

Many of us living in cities don’t give the pipes beneath our streets a second thought – or realise that separate pipes carry stormwater and wastewater from our homes.

Stormwater pipes.

Stormwater downpipes must not go into the gully trap


Stormwater from your roof, driveway and the city’s roads enters the sea untreated. Wastewater, from kitchen sinks, bathrooms and laundries, is piped to treatment plants at Moa Point, Karori and Porirua.

The Council-owned water company, Capacity, uses smoke to find out if there is any cross-contamination between stormwater and wastewater pipes. This involves injecting a dense but harmless smoke into the wastewater main. If smoke emerges from roof guttering, there’s likely to be a misconnection.

Cross-connections between stormwater and wastewater pipes, or leaky pipes, contaminate stormwater with serious effects for the marine environment and pollution of our coastlines. In heavy rain, the treatment plants can then be overloaded because of all the extra water.

Homeowners can help to make a difference by making sure that the downpipes from their roof are not diverted into the gully trap, which takes wastewater.

Capacity will shortly be using smoke-testing in wastewater drains in Kilbirnie.