Numerous questions have been raised on social media following the publication of an RNZ article on Wednesday that warned car owners of a hefty fine they might receive if they washed their vehicles at home.

Individuals discharging contaminants such as cleaning products into stormwater systems face fines of $1500, while companies can be fined $3000, according to infringement provisions set out in the 1991 Resource Management Act.

Local governments nationwide have been asking car owners to wash their vehicles on unsealed ground, such as grass or gravel, or divert the run-off to unsealed ground using sandbags to avoid pollutants entering natural waterways.

While some social media users questioned the fines, others called for more education and awareness, as well as improved designs for new townhouse developments where lawns were sparse.

What follows are answers to some of the most frequently asked questions.

Do the regulations apply in my neighbourhood?

The Ministry for the Environment said 1991 Resource Management Act regulations applied across the whole country, although different councils will have different rules and bylaws.

Councils nationwide cautioned residents to be mindful of what they're putting down the stormwater drain to protect natural waterways.

Officials often took an "education first" approach and would only use fines or prosecutions as the last resort, multiple councils told RNZ.

"[Auckland] Council takes a pragmatic approach towards households, and we do not go out seeking to fine people who may be out washing their cars on a Saturday morning," said Robert Irvine, general manager of licensing and compliance at the council.

"If we were to issue an infringement for such an activity, it would be in response to a complaint and where we believe the activity poses a significant environmental risk."

Local governments have also been engaging with the community to raise awareness.

For example, Tauranga City Council has introduced a water education programme for schools, while Otago Regional Council has launched two programmes titled Only Drain Rain and Adopt a Drain.

James Feary, Three Waters acting unit director at Hamilton City Council, said washing cars on unsealed ground or grassed areas provided a filtration and detention process that allowed soil microbes to break down contaminants.

"It also means the same water is being used to water your lawn, helping water conservation," Feary said.

A spokesperson from the Ministry for the Environment said households should check local government regulations if they were unsure about potentially committing an offence by discharging water or potential contaminants from their property into stormwater systems.

Tauranga City Council uses billboards to raise awareness on ways to reduce pollution in waterways. (Supplied photo)

Are biodegradable cleaning products OK? What if I just use water?

Biodegradable detergents can also pollute waterways, said Jesse Hindt, acting compliance manager at Auckland Council.

A spokesperson from the Ministry for the Environment said using only water or biodegradable products to clean vehicles could still mean contaminants were discharged into stormwater drains.

Radleigh Cairns, drainage services manager at Tauranga City Council, said water used to clean cars often contained sediment, hydrocarbons and heavy metals such as zinc and copper that could be harmful to flora and fauna.

"One car wash might seem harmless, but when tens of thousands of cars are cleaned each week, the cumulative impact is significant," Cairns said.

Can car owners wash their vehicles on grass berms?

If local governments enforced current regulations, car owners might attract a fine for washing vehicles on grass berms if run-off containing contaminants was discharged into drains or street gutters that would eventually make its way into stormwater systems.

Can homeowners clean roofs or the exterior walls of houses with chemical products that might also enter the stormwater drainage system?

The same rules applied when people washed the exterior of their houses or used a water blaster on their property, Feary said.

"People must prevent contaminants from entering the stormwater system," he said.

When washing roofs or houses, even with biodegradable cleaners, either temporarily disconnect downpipes and divert water to unsealed ground, or block drains by using rubber bungs or other devices and remove the wash-water upon completion of works, he said.

"Landowners are responsible for work done on their property," Feary said.

Can homeowners clean their driveway with widely advertised products such as Spray & Walk Away, Wet & Forget and 30 Seconds?

The Resource Management Act stated that people could not discharge any contaminants into water without obtaining consent, Auckland Council's Irvine said.

"In theory, this means that no soaps or chemicals that may cause harm to the environment should be used to wash cars, houses, driveways or any item where run-off can enter our stormwater system."

Can boat owners use cleaning products to wash vessels docked at port?

A clean hull is important to keep a vessel in good shape and having a hull free from hitchhiking pests also helps protect the marine environment, according to Northland Regional Council.

However, the council urged people to use dedicated boat maintenance facilities for routine maintenance, including hull cleaning.

"No hull maintenance can be undertaken on the foreshore," the council said.

"This includes the cleaning, scraping, sanding, blasting, painting or anti-fouling of a vessel hull on the foreshore."

What about homeowners that use a septic tank?

The Ministry for the Environment said septic tanks must meet local discharge requirements, and people should refer to local councils' guidance, rules and bylaws.

Why are the fines for individuals and companies disproportionate?

The ministry said fines for both individuals and companies used to be $750 before amendments to the Resource Management Act were made last year.

"The amendments were made to ensure the regulations continued to be an effective deterrent," the ministry said.

"Increases to a range of infringement fees were based on the ministry's research and feedback from councils and stakeholders gained during public consultation in 2023, and reports from other agencies and councils."

'Only drain rain'

Carla Gee, chief executive at EcoMatters Environment Trust, said it was disheartening for volunteers to see the effects of run-off on water quality when helping to clean up a community stream.

"We understand this is just one part of the wider issues affecting water quality at our beaches, rivers and lakes," she said.

"But the cumulative effect of all residents doing the right thing when washing their cars does make a difference. Remember: stormwater drains only drain rain."

"If people want to understand more about water quality, we, and many other local and regional environmental organisations, always welcome volunteers to join us at local stream clean-up and restoration events.

"This is a great way to contribute to the health of your local awa (river)."