Car Wash Wastewater, Stormwater Drains, and Doing the Right Thing in New Zealand

There has been increasing coverage across New Zealand and local media about councils issuing fines to householders and car detailing businesses for allowing car wash wastewater to enter stormwater drains.

For many people, this comes as a surprise — particularly when they are using products labelled biodegradable. Unfortunately, biodegradable does not mean stormwater-safe, and in most parts of New Zealand the rules are very clear.

This article explains why car wash wastewater matters, what councils generally expect, and what practical options exist for both home users and professional detailers.

Stormwater Is Not Treated Water

In most New Zealand towns and cities, stormwater drains flow directly to local waterways — streams, rivers, lakes, and ultimately the ocean — without treatment.

Anything that goes down a stormwater drain goes straight into the environment, including:

▪︎ Detergents and surfactants
▪︎ Road grime and sediment
▪︎ Oils and grease
▪︎ Brake dust and heavy metals
▪︎ Tyre residue and micro-plastics

Because of this, councils treat stormwater contamination very seriously.

“Biodegradable” Does Not Mean Compliant

One of the most common misunderstandings is the belief that biodegradable car wash products can be safely discharged into stormwater.

Biodegradable products are designed to break down over time in soil, where microorganisms can process them. They are not designed to be discharged directly into waterways.

This is why councils across New Zealand require car wash wastewater to be disposed of onto land, not into drains.

Permeable vs Impermeable Surfaces

Most council guidance is based on whether water is discharged onto a permeable or impermeable surface.

Permeable surfaces allow water to soak into the ground:
▪︎ Grass
▪︎ Soil
▪︎ Garden beds
▪︎ Gravel areas

Impermeable surfaces do not absorb water:
▪︎ Concrete
▪︎ Asphalt
▪︎ Paved driveways
▪︎ Roads and gutters

Washing a vehicle on an impermeable surface where runoff flows into a stormwater drain is generally non-compliant, regardless of the product used.

The Reality of Modern Living

Many people live in environments where land disposal is not straightforward, including:

▪︎ Townhouses
▪︎ Apartments
▪︎ High-density housing developments
▪︎ Properties with fully paved driveways

In these situations, awareness and mitigation become essential.

Practical Options for Home Users

For householders, councils typically expect reasonable steps to be taken to prevent stormwater contamination. Practical options include:

▪︎ Redirecting wash water onto nearby grass or gravel
▪︎ Using runoff diversion devices (often called drain blockers or drain socks)
▪︎ Washing in areas where water naturally flows toward permeable ground

These measures do not eliminate wastewater — but they significantly reduce environmental impact and compliance risk.

There are inexpensive solutions like QuickDam available from retailers like Mitre 10 that seal existing drains and also divert the flow of waste water.

Professional Detailers: Higher Expectations Apply

Professional and mobile detailers are usually held to a higher standard, as wastewater is generated as part of a commercial activity.

Many compliant operators now use:

▪︎ Portable wash mats or inflatable containment systems
▪︎ Temporary “paddling-pool” style wash bays
▪︎ Pumps to collect wastewater into greywater tanks
▪︎ Off-site disposal via approved wastewater facilities or onsite water treatment solutions.

 

Some detailers work with licensed liquid-waste contractors who collect and transport wastewater to approved treatment plants. Others discharge to sewer systems via trade-waste agreements, where permitted.

These systems involve additional cost, but they also provide clarity, compliance, and protection for both the business and the environment.

Responsibility, Not Finger-Pointing

Most stormwater contamination is unintentional. The issue is rarely bad intent — it’s a lack of awareness about where water actually goes.

Understanding where wash water ends up, and taking reasonable steps to control it, dramatically reduces environmental harm and enforcement risk.

The Hermosa Position

At Hermosa, we support:

▪︎ Responsible product use
▪︎ Correct wastewater disposal
▪︎ Practical compliance solutions
▪︎ Industry practices that protect waterways

Clean vehicles should not come at the expense of rivers, lakes, or marine environments. As awareness improves, so does the opportunity to lift standards across the industry.

New Zealand Council Stormwater Guidance

New Zealand Council Guidance on Vehicle Washing

For specific rules and guidance in your area, check your local council’s stormwater or trade waste guidance. Search your council name plus “stormwater vehicle washing” for the most up-to-date local requirements.