Only Drain Rain

Most stormwater isn’t treated before it drains into our local waterways. It’s important to only drain rain and prevent anything nasty getting into our waterways. We need to protect our streams, rivers, lakes and coastal waters.

In the urban environments we have created, rainwater runs into gutters and is collected in stormwater pipes that feed directly into the nearest waterway. Anything that goes into the drains can end up polluting our environment and poisoning fish, animals and plants. This pollution can also spoil waterways for our own use.

Otago Regional Council (ORC) is responsible for looking after our region’s natural resources. To help us do this we have rules that are designed to prevent pollution harming the environment. But it takes more than rules - we need your help to look after our waterways and make sure they are safe for swimming in and gathering kai from, as well as being healthy homes for the plants and fish that live in them.






A wastewater system (also called a sewerage system) collects and removes sewage and wastewater from your house to a treatment plant. During treatment, harmful bacteria, solids and other pollutants are removed so that the water can be disposed of, either on land or out at sea, without damaging our health or the environment.

Wastewater includes water and liquid wastes from hand basins, kitchen sinks, showers, washing machines, dishwashers and toilets.



A stormwater system is designed to prevent flooding by collecting rainwater that runs off roofs and paved areas such as roads, parking lots and driveways.
Stormwater isn’t pure water. As it runs over the ground and paved areas towards a drain it picks up pollutants. So whatever goes into the drain outside your house – whether it’s poured in intentionally or washed down with rainwater – enters our waterways in virtually the same untreated condition.
Some stormwater networks include mud tanks, which filter debris, vegetation and silt from the stormwater, and prevent them entering our waterways.


If we do nothing it could mean:

  • An end to fishing trips and seafood dinners. Shellfish, watercress, eels and other fish can die or become contaminated by toxins washed in via stormwater.
  • The fun we have in and on the water becomes hazardous to our health. High levels of bacteria and poisons in our lakes and harbours due to polluted stormwater runoff could make swimming, surfing and other water sports a thing of the past.
  • Our waterways look like rubbish dumps. Streams and beaches can become blocked or littered with rubbish carried down by stormwater. This is not just unsightly but also a breeding ground for disease and bacteria.
  • Our drinking water makes us sick. Council water supply sources can become contaminated by waterways draining polluted stormwater. This makes our drinking water costly and difficult to treat to safe levels.  


If we only drain rain it will mean:

  • We can eat healthy fish, free of contaminants
  • We can swim in our lakes, rivers and oceans without  the fear of getting sick
  • Our waterways look clean and smell fresh
  • We can trust our drinking water





What you can do at work


What you can do at home

Note: The advice offered here is aimed at urban settings where stormwater and wastewater systems are off-site and serve many properties. It is less relevant to the on-site systems that exist in many rural areas.

Washing your car


Washing cars and equipment on the road or in your driveway means the washwater (and all its pollutants) runs straight into the nearest stormwater drain.



If you wash on a lawn, verge or gravel area the runoff water will be filtered by the plants and soil.

Avoid the pollution risk altogether by using a commercial car wash. Their wastewater is either recycled or goes into the sewerage system and gets treated.

  • Biodegradable detergents still pollute the environment!
  • If washing on a sealed surface is your only option, use a bucket and two cloths – one to wash with detergent and one to polish to reduce the amount of washwater

Tip your washwater down the toilet or sink so it gets treated in the wastewater system, or divert it away from drains (e.g. by using sandbags) onto unsealed ground.


Household DIY


If liquid paint or plaster, cleanup washwater and solvent wastes are tipped into the stormwater drain, the chemicals they contain can kill aquatic life. A little goes a long way!



Work out the exact amount needed to do the job, so you won't have to worry about safe disposal or storage of paint left-overs.

  • Allow plastering waste to dry and then dispose of the solids to a refuse station or via the Council rubbish collection.
  • Use a scraper to clean the bulk of paint from rollers or brushes onto newspaper, then dry this before disposing of it with your rubbish.
  • Rinse the remaining paint from the roller or brush in a 20 litre container filled with water
  • Give them a final rinse in a second container of water
  • Cover both containers and allow them to stand overnight. Once the paint has settled to the bottom, tip the water onto the grass (well away from a waterway), and scrape the paint onto newspaper so it can dry before you dispose of it with your rubbish.
  • Wash water-based paint brushes in the laundry tub (it's connected to the wastewater system not the stormwater drains)
  • Re-use solvents used for oil-based paint brush cleaning by letting the paint particles settle out.
  • Clean up spills quickly and do not hose into the stormwater drains
  • Store all paints, thinners and other liquids in a secure, covered location.
  • Use drip trays in mixing and painting areas and when transferring paint.
  • Return left-over or unwanted paint to a paint shop that has a take-back scheme
  • Store paint and reuse (store can upside down so it forms airtight seal around lid).
  • Dispose of paint or used/unwanted solvents at a refuse station or during Council hazardous waste collection days (not down the wastewater or stormwater systems).


Backyard DIY


DIY clean-up activities like waterblasting and concreting create large amounts of polluted washwater that can end up in the nearest stormwater drain. When cleaning up around the home, think about keeping the environment clean too!



  • Lawns, gravel or garden areas will soak up and filter runoff.
  • Disconnect downpipes (which drain to stormwater) when waterblasting your roof
  • If you're only cleaning off paint flakes and dirt, stretch a filter cloth over the stormwater drain to catch particles and then dispose of the cloth and filtrate.
  • If using chemical additives (eg. moss/mould killers) in your waterblasting you might need to plug a stormwater drain, use it to collect the runoff, and then get it pumped out for disposal. Call your city or district council and speak with their stormwater infrastructure team before starting a job like this.
  • A similar technique is recommended for concreting or asphalting projects that produce wastewater
  • Cut bricks and pavers over a container that can collect the dust/sediment and then dispose of it in your Council rubbish collection.
  • Sweep up debris on the ground to prevent it washing into drains.
  • If rain is forecast, hold off doing any work involving cement, lime or asphalt to reduce the risk of these pollutants getting washed by the rain into stormwater drains.
  • Cover exposed cement, or other materials, with plastic sheeting to prevent it blowing or washing into drains.
  • Adding some porous paving (which lets the rainwater soak into a layer of gravel underneath) to your yard. Bark, shell, paving slabs or gravel are great alternatives to full concrete paths.
  • Planting a raingarden in a low-lying area of your yard to filter rainwater. For advice on how to create one contact your local Council or garden centre.
  • Installing a rain tank. Collecting rainwater reduces the risk of flooding during heavy downpours and eases the demand for water in dry spells. Win - win!
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