How to wash your car without polluting drains and rivers
By Sam W - SoapX Ltd.
The drain at the end of your drive probably does not go to a treatment works. In most streets it runs straight to the nearest stream or river. A few small changes keep your wash water out of it.
Two kinds of drain
Most UK homes are served by two separate systems.
- The foul sewer takes waste water from sinks, toilets, baths and washing machines to a treatment works, where it is cleaned before it is released.
- Surface water drains take rain from roofs, driveways and roads. That water gets no treatment. It goes directly to rivers and beaches.
The gullies in the road and most drains on a driveway are surface water drains. Whatever runs into them ends up in the local river as it is. Some older areas have a combined sewer that takes both, but you cannot tell by looking, so treat every outdoor gully as if it leads to a river.
What is in car wash water
- Detergent from snow foam and shampoo.
- Oil, fuel residue and road film.
- Brake dust, which carries metal particles.
- Road salt and grit in winter.
None of that belongs in a stream. Detergents can harm fish and insects even when a product is biodegradable. Regulators describe biodegradable, phosphate free products as less harmful to the environment. They do not describe them as harmless.
What the rules say
For businesses the position is clear. Environmental regulators tell anyone washing vehicles commercially that run off must not enter surface water drains, rivers or ground water, and that they can be prosecuted if it causes pollution. That is why a proper car wash drains to the foul sewer or recycles its water.
A householder washing one car is a much smaller source, but the same drains and the same rivers are involved, and causing pollution can be an offence whoever does it. The sensible approach is to keep as much wash water out of the road drain as you reasonably can.
How to wash at home with less run off
- Pick your spot. Wash on gravel or grass if you have it, or on a part of the drive that drains onto a lawn or border. Soil filters and breaks down small amounts of wash water far better than a river can. Stay well away from ponds, streams and ditches.
- Use the label dilution. More product does not mean more cleaning. It only means more detergent in the run off. Our dilution ratio calculator gives the exact amounts.
- Use less water. A pump sprayer for pre rinse and the two bucket method use far less water than a running hose, so less leaves the drive.
- Choose the mildest formula that does the job. Keep the Extreme formulas for heavy soiling and use Summer or Delicate for routine washes.
- Empty buckets indoors. Pour leftover shampoo and rinse water down a sink or toilet, which lead to the foul sewer. Never tip a bucket into a road gully.
- Keep the car protected. Paint with a sealant on it releases dirt with less product. No.08 Wax and Sealant takes minutes to apply.
Jobs to keep off the drive
- Engine bays and oily parts. Oil is the worst thing to send down a surface drain. Use a drip tray and rags, and take oily waste to your local recycling centre.
- Chains and drivetrains. When you use No.04 Drivetrain and Chain Degreaser, work over a tray or old cardboard to catch the drips, and keep the residue away from the road drain. Our chain cleaning guide shows the routine.
- Very muddy vehicles. After a track day or a green lane, use a jet wash bay. Commercial wash bays should drain to the foul sewer or recycle their water.
Quick answers
Is it illegal to wash my car at home?
Washing your own car at home is not banned. What the law targets is pollution. If wash water causes pollution in a river, the person responsible can be prosecuted, so it makes sense to keep it out of surface drains.
How do I know where my drain goes?
You usually cannot tell by looking. Your water company or local council can tell you whether your street has separate or combined sewers.
Are biodegradable products safe for rivers?
No product should go into a river. Biodegradable means it breaks down over time, not that it is harmless to fish while it does.
Is a commercial car wash better for the environment?
A properly run one is, because its waste water is treated or recycled. For a regular light wash at home, the steps above keep your impact small.
This guide is general information and not legal advice.
Kit for this job
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