Stormwater and the sewer system


Under the streets, towns and villages of the Shoalhaven there are two main underground systems which carry our unwanted water, the sewer system and the stormwater system.

While Shoalhaven Water manage the sewer system, stormwater is managed by Shoalhaven City Council.

Report any stormwater related issues to Council using the online Report a Problem link.

The difference between sewer and stormwater drainage

Sewer (or wastewater) is the used water that comes from your kitchen, bathrooms, laundry, sinks or other plumbing components in your home. Sewer systems collect, treat and dispose of the sewer from our homes and businesses.

Stormwater systems are made up of gutters, downpipes, pits and drains which collects any water which runs off a site due to rainfall. Stormwater systems manage rainwater run-off from our streets and roofs. Stormwater should never be plumbed into the sewer system as this can cause serious overflows. 

These two systems are supposed to be separate and when stormwater gets into the sewer system the extra water can lead to an overflow of diluted raw sewer.

Overflows are a serious source of pollution, a potential health risk and a nuisance to both the community and Council.

There are two ways for storm water to get into the sewer system:

  • Infiltration – usually caused by cracked or broken underground pipes which can be difficult to detect; and 
  • Inflow – a direct flow of rainwater usually from an illegal roofing downpipe that has been directly connected to the sewer system.

Common ways stormwater can get into the sewer system

Cracked Pipes – usually caused by tree roots or movement in the ground.

Low-lying Gully – these are found just outside your house and generally have a loose-fitting grate that comes off easily in the instance of a sewer overflow. If the gully is low-lying in the ground then it can let large amounts of stormwater into the sewer system. A plumber can raise the gully or lower the ground around it.

Direct Connection – stormwater pipes are not allowed to be connected to the sewer system. The effect of excess water in the sewer system can cause overflows of raw diluted sewer further down the system.

Inspection Holes – poorly fitting, cracked or broken inspection holes can let water into the system. If you notice any problems contact Shoalhaven Water directly.

Broken Pipes – broken pipes can occur in both Council’s sewer systems and on private property. Whilst Council will maintain the mains, as a property owner it is your responsibility to maintain the pipes on your land. Broken pipes not only let stormwater in, they can cause a health impact on the environment. Contact a licensed plumber immediately.

Boundary Traps – are inspection points in the sewer system and mark the place where your system joins Council’s mains. Damaged or cracked lids and/or concrete rims will allow unwanted stormwater water to enter the system. There will also be a problem if the vertical riser (the pipe under the boundary trap) is cracked.

Keeping stormwater out of the sewer system

An overflowing sewer can be unpleasant and anyone who has had the experienced usually remembers it. Sewer overflows effect everyone, they cost money to clean up and they damage our environment. By working together, we can help keep stormwater out of the sewer system.

As a property owner you are responsible for maintaining the internal pipes on your property so that stormwater doesn’t leak into the sewer system.

If you are unsure if stormwater is getting into your internal sewer system there are a number of tests that can be conducted to find where potential issues may be including:

  • Camera investigation – a remote control CCTV camera can be inserted into the pipes to check what condition they are in; and/or
  • Smoke testing – which is non-toxic smoke directed into the sewer pipes and typically smoke will come out of any inappropriate connections or breaks to pipes.