Run-off into drains, septic tanks, reed beds, streams, rivers, marinas & lakes – the environmental impact

March 22, 2024 3 Comments

Soft washing near river & stream

A question our customers often ask:
"What should I tell my customers who want to be re-assured that run-off from soft washing will not have a detrimental effect on our environment?"

Firstly, prevention is better than cure so reduce run-off at source by using skillful application techniques. Using the correct nozzles and flow rates will also significantly reduce run-off and therefore will reduce risk to our environment.

Soft washing a property that close to a stream, river, lake, or marina

Customers can be especially concerned if their property is close to a stream, river, lake or marina.

Soft washing near marinas & lakes

Check with the owner of the marina/lake as to what chemicals that are legally allowed to be discharged into the water.

Check with the local water authority and ask for their guidance because UK regulations differ from county to county. EU regs state that a one-off chemical discharge may be considered ok, but after Brexit in the UK it’s necessary to check the local regs.

Your options are:

1) Pressure wash only

2) Lightning Cleanze and Tornado Cleanze, from which the run-off will contain only a small amount of salt and the biodegradable surfactant,

3) Bio Cleanze, which is fully biodegradable.

Quick tip: According to the strict letter of the law even the run-off from pressure washing alone needs to have permission to enter a fresh watercourse because it may contain pollutants from the removed dirt and grime.

Give the marina/lake owner and water authorities our product SDS sheets so they know the precise nature of our products. Ask for their advice and proceed accordingly.

Whatever route you take, skilful application using Benz softwash nozzles will minimise spray drift and run-off into the water.

Soft washing near rivers & streams

The safest option if a property is close to a river would be to use Benz Bio Cleanze only, which will remain in the treated porous surface, offering long-term residual biocide protection from re-colonisation.

Bio Cleanze is fully biodegradable without further treatment and does not bio-accumulate. And as this product should not be rinsed, there is no concern about rinse water entering drains or the river.

There's seldom an issue when treating with Bio Cleanze because there is very little run-off when skilfully applied.

Your customer would have to accept the longer timescale for results to show than if Benz Lightning Cleanze was used first to clean the worst of the contamination.


Lightning Cleanze does not bio-accumulate and it's surfactant is fully biodegradable.

Even so, run-off from Lightning Cleanze should not go into surface drains, which often lead into rivers.

The rinse water will only contain very small amounts of common salt and organic residue. But it should be diverted to the foul water drain where it will be treated by the local sewage works.

Most properties have sewer access near the paths, so it's usually a simple matter to divert the rinse water into the foul water system.

Quick tips:

  • Properties built prior to 1950 in the UK will probably only have foul water drains.

  • If no foul drain is available, or the local water authorities will not allow it to be used, suck up the rinse water and remove from the site in suitable containers. Then dispose of safely.

More suggestions for the safe treatment of chemical run-off and rinse water:

  1. First determine if the drains are foul or surface water drains.
  2. If foul, there is not usually a problem.
  3. Always check with the local water authority as to what they allow to go into their drains, as the regulations vary throughout the country.

Quick tip: EU regulations allow for one-off discharges of some cleaning products into drains. It is the continual or regularly repeated discharge that harms the environment. The UK regs are usually similar but it would be wise to check.

Ask for permission from the water authority to dispose of rinse water into a surface drain. Quote regulation "ERC 8E" from the “REACH Use Descriptor System” when making your application.

Block and/or divert downpipes

When treating a roof with Bio Cleanze the amount of run off can be minimised by using skilful spray techniques and Benz spray nozzles

  • Downpipes can be temporarily blocked with rags and a tennis ball. Run-off from roofs can then be sucked from the gutters.
  • Prior to removing the tennis ball, run-off can be further diluted with tap water  before allowing it to flow into the downpipe.
  • Downpipes can be disconnected and used to flow the run-off into suitable containers for safe removal from the site.
  • The downpipe can often be diverted into a foul drain (not a surface drain).
  • Diverting the downpipe into a container means you can use up the run-off by giving a quick free clean of your customer's paths (with their permission), avoiding the time and expense of having to dispose of it elsewhere. A nice win-win for contractor and customer.

Erect dams (aka "Berms" "Dikes" and "spill containment barriers" ) to contain soft wash chemical run-off

Contain the run-off by building dams around the area being treated (using easily available non-absorbent barrier products such as these on Google). Then suck up the run-off with an industrial suction machine.

Quick tips:

1) Rinse water can be brushed to a safe (no access by humans or animals) on-site area to evaporate and/or be sucked up. In hot weather the collected run-off can evaporate quickly, reducing the quantity needing to be removed from site. So the most effective work system can be to schedule final removal of the collected run-off as the final job of the day.

2) Because environmental legislation and building regulations are continually changing it is wise to check with the relevant local authorities as to their current guidelines, and ask if they want any particular procedures put in place. The information in this article and video pertains to EU and UK legislation and is our best understanding of the situation at the time of writing.

IMPORTANT: Septic tanks and reed beds should never have any run-off or rinse water from any chemical fed into them.

Click here to get more practical soft washing how-to tips

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "how to" – into our in-site Search Engine (magnifying glass icon on the main menu).

You can order Benz Softwash chemicals & equipment online or by phone:

GB (England, Scotland, Wales)

Phone: 0800 70 74 222 


Ireland and other countries

Phone: 00353 214 622 978


Lines open Monday - Friday, 9am – 5pm

Please note: The above numbers are for orders only (click here for tech support)

We hope this information is helpful and sincerely wish you great success in your soft washing business,

Benz Team

PS: After completing the first soft wash treatment, put your customer on a "Clean & Maintain" ongoing maintenance programme. Your customers will enjoy a permanently clean property and you will enjoy a steady stream of repeat business.

This is clearly a win-win arrangement for both customer and contractor.


Click here to explore the extensive range of Benz softwash cleaning chemicals & equipment

Benz Softwash Bio Cleanze DDAC biocide & Benz Softwash Lightning Cleanze SH sodium hypochlorite biocide

3 Responses

Ben Hawkins
Ben Hawkins

April 02, 2024

Hi Mr Morgan,

Please email with your request and one of our team will get straight on it.

Ben Hawkins
Ben Hawkins

April 02, 2024

Hi Mr Morgan,

Please email with your request and one of our team will get straight on it.

Mr  Morgan
Mr Morgan

April 02, 2024

I have unsightly red stain stains. On the outside front render of my cottage,, I live in the Isle of Man. Is there anyone in my area qualified and experienced to use your system here . Would like contractor information and advice on costs please
Mr C Morgan


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