What you need to know about stormwater drains

A big part of protecting our environment is to stop pollutants reaching our harbour - so the Council has introduced a Stormwater Bylaw to help reduce a range of pollutants entering the stormwater system, which flows untreated into our streams and harbour.


Frequently Asked Questions


What is banned from stormwater drains?

These common household pollutants are now banned from going in the stormwater system:

  • Cleaning products - including detergents and disinfectants, such as bleach, and '30 Seconds' type of outdoor cleaners
  • Paint and solvents - including turps and paint stripper
  • Water blasting waste
  • Liquid fuels - petrol, diesel, etc
  • Motor oil, grease and radiator coolant
  • Cooking oil
  • Cement wash, cement slurry, concrete cutting waste - this includes wash from new exposed aggregate driveways


How do I dispose of banned pollutants safely?

Tips for safe disposal:

  • Cleaning products – tip wash water either down sink or dispose to your lawn or garden. Take any un-needed cleaning products to the landfill in a sealed container. See our tips on cleaning your car below.
  • Water blasting waste – water run-off can go into the garden or lawn. Paint flakes should be collected and put in your household rubbish. Older houses may have lead-based paint, so always collect and dispose of carefully.
  • Solvents and liquid fuels - take in sealed container to the landfill. A small charge applies for safe disposal.
  • Cleaning paint brushes – water-based paint can be cleaned from brushes in your laundry sink. Solvents used to clean oil-based paints from brushes - leave the solids to settle out, then re-use the solvents. Take any excess solvents to landfill in closed container for safe disposal (a small charge applies).
  • Leftover paint - small amounts of paint can be left to dry and disposed of with household rubbish. Check with your local paint store about products to harden waste paint for easy disposal. Paint tins in reasonably clean state can go into your recycling. Leftover paint can be taken to the landfill or Resene Colorshop in Porirua for recycling, reuse or safe disposal. Resene also donates leftover paint to community groups and safely disposes of material that cannot be recycled. Dulux Trade Centres in Lower Hutt and Wellington City have a Paint Take-Back service as well. A small charge may apply for these schemes, depending on the brand and type of product and amount you have leftover.
  • Motor oil, grease and radiator coolant – take to the landfill in a sealed container for safe disposal.
  • Cooking oil - wash small amounts down the sink. Larger amounts put into the garden/compost or to the landfill.
  • Cement wash, cement slurry, concrete cutting waste - this includes wash from new exposed aggregate driveways – wash should be channelled to the garden. Small amounts of slurry or waste can be tipped to the garden to harden and then disposed of with the household rubbish collection. Large amounts should be collected and taken to the landfill.
  • Any other chemicals labelled as dangerous - always take in sealed containers to the landfill and discuss with the staff on duty.


How else can I help reduce harbour pollution?

  • Report pollution incidents immediately to the 24 hour Environment Hotline on 0800-496-734.
  • Adopt a drain – locate the nearest stormwater drain to your house and help to keep it clear of leaves and rubbish, so that rainwater can move freely into it - helping our stormwater system work properly in heavy rain.
  • Recycling – if using an open recycling bin, bag light items like plastic and paper together to weigh them down on windy days.
  • Litter & dumping of rubbish – Please pick up any loose rubbish you see and report any dumped rubbish immediately to the Council Phone (04) 237 5089:
    • Bags of nappies and other rubbish are sometimes thrown down stream banks and left in parks – where germs and chemicals can leach into our waterways and harbour.
    • Many hundreds of tyres have been extracted at high cost from the harbour during clean-ups. Always dispose of tyres to the landfill (a small charge applies).
    • Road cones and supermarket trolleys – do not throw these into streams and the harbour! It may seem like fun at the time, but it creates a big clean-up cost and encourages further littering.
  • Dog droppings – always put into the rubbish or bury. Please keep the front of your property free of droppings, even if left there by someone else's dog. Do not move droppings into gutters or stormwater drains, as they carry many germs that cause serious health risks once in our waterways and harbour.
  • Join a local environmental group, programme or event - see details further below.


Why is car washing bad for the harbour?

  • Run-off from washing vehicles contains pollutants including detergents, dirt, oil and heavy metals that are ecotoxins and/or carcinogenic. If the run-off goes into a stormwater drain, it will empty untreated directly into our streams and harbour - which is bad for aquatic and marine animals and plants - and harbour users.
  • A local survey has shown that nearly half our households wash their vehicles on driveways. With at least 58,000 cars across the Porirua harbour catchment (Census 2013 estimate), the cumulative effect of run-off from even a portion of these vehicles going into stormwater drains is significant.
  • Car washing is usually a fine-weather activity, when stream flows are lower so that contaminants will be more concentrated and less likely to flush out of streams and the harbour.
  • A significant amount of pollutants accumulate on our roads. Luckily when raining, these road contaminants are diluted and more likely to be flushed out of streams and the harbour than pollutants tipped into drains during fine weather. The NZ Transport Agency, Regional Councils and others are undertaking research to understand and address the issue of road run-off nation-wide.

How should I wash my car at home?

It's fine if you already wash your car somewhere where the water doesn’t flow to the stormwater system. Otherwise follow these simple tips:

  • Where possible wash your car on grass or divert the wash water from your drive or road using something like old towels to intercept the run-off and channel it into the garden or grass.
  • If you can't divert the run-off, please use a bucket and cloths rather than a hose – this will reduce the water run-off
  • Dispose of dirty water correctly - empty the dirty water into your laundry sink or gully trap so that it goes into the wastewater system to be treated.
  • There are some eco-friendly carwash detergents that can be used which are better for the environment (especially ones that are low in phosphates). Phosphate is a fertilizer and promotes the growth of nuisance algae in our streams and harbour which has a negative impact on animals and other plants.
  • You can wash your car on the public grass berm.

Where else can I wash my car?

  • Go to a commercial car wash, where run-off is collected and treated, it doesn’t go into the stormwater system.
  • Go to a community carwash fundraiser – as the Council will be working with these groups to continue with these events, but in a more environmentally-friendly way.
  • The Council is considering a number of potential locations for several public car washing pads over the longer term, in consultation with local communities.

Can I wash my car just with water?

  • If you wash your car without detergent, there are still many pollutants in the grime being washed off.The Council encourages you to avoid all carwash run-off entering stormwater drains. However, if you wash your car only with water (ie no detergent), then the run-off is not strictly speaking banned from going in the stormwater system.


Why don’t you send the stormwater to the treatment plant?

The simple behaviour changes promoted above are the most practical and least costly way to reduce harbour pollution from common household chemicals.

  • There are over 72 stormwater outfalls around Porirua Harbour alone and many more discharging to our streams. Sending stormwater to the Wastewater Treatment Plant is not feasible, due to the huge amount of rainwater that would need to be captured and pumped for treatment from these outfalls. The Treatment Plant could not cope with the extra water, which would lead to dangerous overflow issues when it rains and also dilute the microorganisms needed at the plant to digest wastewater. The scale of infrastructure change needed would also be too costly to fund, including reconnecting the entire network, building many new pump stations and increasing the size of the Treatment Plant considerably.
  • Treating stormwater just before it discharges to streams and the harbour would not be financially or technically feasible in Porirua, due to the high number of outfall locations and insufficient land for treatment facilities to be built.


What stormwater pollution problems should I report?

  • Report any pollution problems (land, air or water) to the 24hr Environment Hotline on 0800-496-734 immediately. That way the source can be tracked down and remedial action taken. This service is managed by Greater Wellington Regional Council.
  • For other concerns or queries, please contact Porirua City Council - Phone (04) 237-5089 or email enquiries@pcc.govt.nz.

Are you going to prosecute people?

  • Flagrant/serious offenders will be prosecuted if they are directly pouring/spilling/washing contaminants into the stormwater system.
  • The Council isn’t asking neighbours to ‘dob’ one another in for minor matters. However, the Council will continue to respond to complaints and queries as it does with other areas it regulates.


What other harbour work is done by the Council?

The Council is focused on raising awareness that the stormwater system flows untreated to streams and the sea - and encouraging people to take a part in improving the environment. The new Stormwater Bylaw works alongside other bylaws and programmes important for harbour protection, eg:

  • Te Awarua-o-Porirua Harbour and Catchment Management Programme
  • Te Awarua-o-Porirua Whaitua Committee
  • The Silt and Sediment Control Bylaw which targets building and development sites to reduce silt ending up in the harbour.
  • The Wastewater Bylaw (pdf) that ensures septic tanks and domestic wastewater treatment systems are installed and maintained properly.
  • The Trade Waste Bylaw (pdf) that ensures liquid waste from commercial and industrial users is disposed of correctly via the wastewater system.
  • Schools - funding school environmental education programmes.
  • Transmission Gully Motorway - there may be short-term impacts on the harbour from sediment during the construction phase of the motorway, which will be managed carefully. But once built, the motorway will likely provide long-term benefits to harbour health.
  • Wellington Water - provides long-term strategic asset planning and maintenance of the Wellington region's water, stormwater and wastewater networks and is jointly owned by Greater Wellington Regional Council, Porirua City, Wellington City, Upper Hutt and Hutt City councils. To find out more: Wellington Water.


What local environmental groups, events and programmes are there?

Getting involved in local environmental initiatives is a great way to help keep Porirua beautiful: