Stormwater and the Sewerage System

While Shoalhaven Water manage the sewerage system, stormwater is managed by Shoalhaven City Council. Report any stormwater related issues using the online Report a Problem link. 

Overflowing sewer manhole

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

How do I know 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. Sewerage systems collect, treat and dispose of the sewage 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. These pipes and drains connect to your roof, driveway, garden, paths and roads. Stormwater should never be plumbed into the sewer system as this can cause serious overflows. Stormwater systems manage rainwater run-off from our streets and roofs.

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

Common ways stormwater can get into the sewerage 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 sewerage 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 sewerage system. The effect of excess water in the sewerage system can cause overflows of raw diluted sewage 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 sewerage 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 sewerage 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 sewerage system

An overflowing sewer can be unpleasant and anyone who has had the experienced usually remembers it. Sewerage 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 sewerage system.

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

If you are unsure if stormwater is getting into your internal sewerage 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.