Our Mission: Cleaner Cars, Cleaner Waters — Why We Insist on Using Designated Car Wash Stations

Every time a car is washed, something else is being washed away too — not just the dirt, grime, and road film on your vehicle, but micro-amounts of oil, heavy metals, brake dust, rubber particles, detergents, and chemicals. Unless that wastewater is properly collected, treated, or recycled, it can run off into the surrounding environment, contaminating waterways, harming aquatic life, and degrading ecosystems.

At the Dip Stage, we believe in a simple but powerful principle: wash your car at facilities designed to protect the environment. Below is a deeper look at why this matters, what scientists have found, and how we can work together to make New Zealand cleaner.

Why home or driveway car washing is risky for the environment

When vehicles are washed on driveways, in front yards, on unsealed surfaces, or in public spaces where wastewater is not managed:

• The runoff often flows directly into stormwater drains, which commonly discharge untreated into streams, rivers, lakes or the sea. The wastewater bypasses any purification or treatment. EPA+2FLEX Car Wash+2

• The wash water is a cocktail of pollutants:
    • Detergents and surfactants (used in soaps and degreasers) can be toxic to aquatic organisms, damaging fish gills, killing eggs, and disrupting cell membranes. gjesm.net+4Ask IFAS - Powered by EDIS+4FLEX Car Wash+4
    • Oils, greases, hydrocarbons from the vehicle surface accumulate in the wash water. PMC+4gjesm.net+4ResearchGate+4
    • Heavy metals (zinc, lead, copper, nickel, chromium, etc.) originate from brake wear, tire wear, engine parts, metal alloys, road dust, and atmospheric deposition. gjesm.net+3ResearchGate+3ScienceDirect+3
    • Suspended solids, particulates, microplastics — washed off the bodywork, tires, and undercarriage — increase turbidity and block light in waterways. Deswater+2ResearchGate+2
    • Nutrients (phosphates, nitrogen compounds) from some cleaning agents can feed excess algal growth (eutrophication), depleting oxygen and harming aquatic life. ResearchGate+3EPA+3FLEX Car Wash+3

Because of this, the “innocent-looking” act of washing a car can become a conduit for pollution.

One municipal best-practice guide sums it up: “Outdoor car washing can cause detergent-rich water to flow into storm drains … Car wash facilities minimize stormwater impacts and are safer than residential washing.” EPA

In New Zealand, regional environmental authorities require that any business or site generating wash water must collect and properly treat or dispose of it — otherwise they are contributing to pollution and may be breaking legislation. Environment Southland

What the scientific and engineering research tells us

Over the past decades, researchers have studied car wash wastewater (often referred to as “CWW”) and treatment approaches. Here are key findings:

1. CWW is heavily polluted

   • A review of 68 research papers showed that car wash wastewater generally has very high concentrations of suspended solids (SS), oil & grease (O&G), chemical oxygen demand (COD, a measure of organic pollution), turbidity, and surfactants. ResearchGate

   • Another systematic review observed that CWW often contains heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other harmful compounds. ScienceDirect

   • Studies of CWW in multiple settings reveal that pollutant concentrations often exceed environmental discharge limits — sometimes by a wide margin. gjesm.net+3ScienceDirect+3gjesm.net+3

2. High water usage, and large total pollution loads

   • In one field study (in Ghana), seven car wash stations together used 2,395 to 15,480 L/day depending on vehicle mix. ScienceDirect+2PMC+2

   • In that same study, average water used per vehicle was ~158 L for a standard sedan, and up to ~370 L for a bus/coach. ScienceDirect+1

   • The total pollutant loads (COD, metals, solids) discharged untreated are substantial. For example, COD loads in the study reached many tons per year. ScienceDirect+1

   These numbers underscore that even though each wash is “just one car,” the cumulative impact across many vehicles adds up to a severe environmental threat.

3. Effective treatment and reclamation is possible, but technically challenging

   • Many car wash systems now incorporate coagulation / flocculation, membrane filtration (microfiltration, ultrafiltration, nanofiltration, reverse osmosis), adsorption, biological treatment, or hybrid combinations. These can remove high percentages of suspended solids, oil, and organic pollutants. Deswater+3PMC+3ResearchGate+3

   • For example, combining coagulation with membrane filtration has achieved >90% turbidity removal and 50-95% reduction in COD in some studies. PMC+2MDPI+2

   • Some advanced designs integrate Microbial Fuel Cells or Metal-Organic Framework (MOF) materials to enhance pollutant removal. ScienceDirect

   • However, challenges include sludge disposal, energy use, initial capital cost, maintenance, and the balance between water recovery and treatment effectiveness. Deswater+4PMC+4ResearchGate+4

   • In fact, a review concluded that combining multiple techniques is often the most viable path to efficient and cost-effective on-site treatment. ResearchGate+1

4. Recycling and reuse dramatically reduce water demand

   • Well-designed car wash facilities can reclaim and reuse up to 80–90% of wash water, dramatically lowering fresh water demand. 8374610.fs1.hubspotusercontent-na1.net+3QC | Capital+3Aqua Bio+3

   • In professional operations, “freshwater use per vehicle” benchmarks as low as 30 gallons (~113 L) have been reported in systems using reclaim cycles. 8374610.fs1.hubspotusercontent-na1.net+28374610.fs1.hubspotusercontent-na1.net+2

   • Water reuse systems not only conserve water but reduce the volume of wastewater needing treatment or discharge. Deswater+3Aqua Bio+3waterpurificationcenter.com+3

5. Environmental & ecological risks from untreated discharge

   • Untreated car wash effluent can exceed regulated discharge limits by many times, threatening aquatic ecosystems. Deswater+3ScienceDirect+3gjesm.net+3

   • Heavy metals in car wash runoff — such as lead (Pb), copper (Cu), zinc (Zn), and chromium (Cr) — pose serious ecological risk. In one study, Pb levels in car wash effluent were deemed to be “extreme pollution.” PMC

   • Runoff with high levels of COD, nutrients, and suspended solids contributes to oxygen depletion, habitat smothering, loss of biodiversity, eutrophication, and bioaccumulation of toxic metals. ResearchGate+3MDPI+3gjesm.net+3

   • Long-term accumulation of metals and chemicals in sediment and soils can lead to persistence in the environment, affecting organisms over time. gjesm.net+2gjesm.net+2

In summary: the science is clear — car wash wastewater is pollutant-rich, likely to harm water bodies if unmanaged, and yet treatment technologies exist. The missing link is often infrastructure, oversight, and incentives.

Why washing at designated professional car wash stations matters

Given the risks, here’s why we (and environmental agencies) strongly encourage — and sometimes mandate — washing vehicles only at properly equipped car wash facilities:

1. Capture and containment
   Professional washes generally operate on impervious concrete bays connected to drainage systems that lead to collection sumps, oil/water separators, and treatment systems rather than into storm drains. This ensures wash water is contained and handled rather than being allowed to runoff into the environment.

2. Treatment, filtration, and disposal
   These facilities are more likely to treat, filter, or recycle that collected water. Contaminants like oil, solids, and chemicals can be removed before discharge or reuse. Some systems meet local regulatory standards before releasing any effluent.

3. Water recycling / reuse
   By reclaiming a large fraction of wash water, these stations drastically reduce freshwater demand, making the process more sustainable and less wasteful.

4. Use of safer chemicals
   Many professional washes now use biodegradable, pH-neutral, phosphate-free detergents and cleaning agents, reducing the risk of chemical harm downstream.

5. Regulation and compliance
   In many jurisdictions (including New Zealand), commercial and industrial activities that discharge wash water must comply with environmental rules, permits, or conditions. Washing at a facility that is licensed and monitored helps ensure environmental compliance. (In contrast, individuals washing cars at home or in driveways may unintentionally break local regulations without knowing it.)

6. Economies of scale and best practice
   A dedicated facility can amortize investment in high-efficiency pumps, treatment, and infrastructure in a way that would be impractical on the household level. This means using less water per car, more effective pollution control, and professional operations.

By doing so, professional car washes turn what would be a pollution source into a managed process — preserving water quality, aquatic life, and community health.

Framing the message for New Zealand

While much of the published research is from overseas, the principles apply here in New Zealand, and there is local regulation and guidance:

• Environment Southland’s guidance document explicitly states that wash water from businesses must be collected and properly treated or disposed of to avoid polluting land, streams, or groundwater — otherwise the business is contributing to pollution and breaking the law. Environment Southland

• New Zealand’s freshwater is a precious resource, especially in light of climate change, droughts, and competing water demands. Every litre saved and every contaminant avoided helps protect our rivers, lakes, and coastal keystone environments (estuaries, wetlands, marine zones).

• New Zealanders value clean waterways (for recreation, fishing, biodiversity). Encouraging the public and vehicle owners to choose eco-aware car wash facilities aligns with national values of kaitiakitanga (guardianship) and environmental stewardship.

Summary

OUR MISSION: Wash Responsibly, Protect Aotearoa’s Waters

Every time a vehicle is washed, pollutants such as oils, heavy metals, brake dust, detergents, and fine particulates accumulate in the runoff. If washed on driveways or open ground, that contaminated water flows directly — untreated — into stormwater drains and natural waterways, threatening aquatic ecosystems, drinking-water quality, and biodiversity.

Designated car wash facilities offer an alternative: one that actively protects New Zealand’s environment. At professional car wash stations:

• Wash water is captured, not allowed to run off to streams.

• The water is filtered, treated, and sometimes recycled, removing oils, heavy metals, solids, and chemical residues before any release.

• Reuse systems can recover 80 % or more of water, reducing fresh water demand and environmental strain.

• Biodegradable, low-impact cleaning agents are used, minimizing chemical harm.

• Operated under environmental licensing and best-practice standards, these facilities help ensure compliance with local laws and protect our waterways.

Scientific studies confirm that untreated car wash runoff is a significant source of pollution globally. Research shows high concentrations of heavy metals, surfactants, oils, and sediments in car wash wastewater — often exceeding safe levels if discharged untreated. Treatment and recycling systems exist and can dramatically reduce that pollutant load.

By choosing to wash your vehicle at an approved car wash station, you help safeguard New Zealand’s lakes, rivers, groundwater, and marine environments. Together, we can uphold our shared value of Kaitiakitanga — the guardianship of nature — one clean wash at a time.