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Save the drain for rain

Save the drain for rain

Updated 26 November 2019 1:33pm

In urban areas, the pipes that collect rainwater from your roof and yard are connected to a network of underground pipes that transfer the rainwater to local streams or to the seashore. These pipes are the stormwater system. There is a separate system of pipes that transfer wastewater from the toilet, bathroom, kitchen, and laundry to a sewage treatment plant. These pipes are the sewerage system.

In areas without stormwater systems, rainwater from roofs and driveways may drain into soak holes. In areas without sewerage systems, wastewater is generally treated in a septic tank.

It is illegal for stormwater to go into sewers. It is illegal for anything other than rainwater to go into stormwater drains. If wastewater or other liquid household wastes (see table below) get into the stormwater drain, they will pollute streams, aquifers or the sea.

So how do you know whether a drain is connected to the stormwater or sewer system?

Domestic sewer gully traps:

  • Receive wastewater from inside the house (bathroom, kitchen, laundry)
  • Should be raised above ground level to prevent surface water getting in.
  • Water in the gully may be smelly or dirty.

Domestic stormwater drains:

  • Receive water from outside the house (roof downspouts, yards etc)
  • May be at ground level for yard rainwater drainage.
  • Water should be clean, with no bad smell.

Here are some suggestions for how to dispose of some common household wastes and avoid pollution


Good disposal options

Leftover paint and paint brush wash water Leave small amounts of unwanted paint to dry in the tin, then dispose of the tin with your household rubbish. For large amounts of unwanted paint, take it to the recycling centre at the landfill.
Pour wash water from paint cleaning down the laundry sink or sewer gully trap, or onto soil in your garden.
Paint fragments and paint stripper Sweep paint scraps up with a broom, then dispose of them with your household rubbish. If using a water blaster, try to stop scraps entering the drain. When using paint stripper, remove residues with a rag and then wash off the stripped surface over soil or on the lawn.
Used engine oil and radiator water Ask your local garage if they accept used oil for recycling, if they don't, check with your local council. Otherwise, put it in a sealed container and take it to the hazardous wastes area of the landfill. Radiator water should also be taken to the hazardous wastes area of the landfill.
Oil spills and leaks Mop up with rags, sand or soil. Remove residual oil with some bleach or detergent, then soak that up with rags. Dispose of any waste with your household rubbish. don't hose it away because even a small amount of oil will cause a problem when it reaches the stream.
Wash water from cleaning your car Minimise the amount of detergent you use. Wash the car on the lawn or at a car wash, rather than on the road or driveway where wastewater can go down the gutter into the stormwater system.
Waste cement or concrete For small quantities, pour wet cement or concrete onto soil and let it harden as small lumps. These can be disposed of with your household rubbish. Larger quantities can be buried in your garden, or taken to the landfill.
Driveway, path and yard sweepings Collect the sweepings and add them to your compost or dispose with your household rubbish. don't hose rubbish from your property onto the street or down the drain.
Waste pesticides Ask your local council if it has any special arrangements for the collection of waste pesticides.

Remember, the only thing that should get into the stormwater drain is rainwater. You can be fined for putting anything else down the drain.

Some effects from these kinds of contaminants:

Waste oil Oil causes unsightly surface slicks on the water in the stream or the harbour. In large quantities it can suffocate aquatic life.
Paint Paints (oil and water based) and thinners are toxic to aquatic life, and cause discoloration of streams.
Wash water Detergent causes foaming and nutrient enrichment of streams, and is toxic to aquatic life.
Dirt and silt Dirt and silt smother aquatic life on stream beds and the sea floor, and cause discoloration of stream

Keep the streams and the sea healthy by following these suggestions.

If you see somebody dumping wastes into the stormwater drain, call your local council, or the Greater Wellington Regional Council Pollution Hotline 0800 496 734.