How Businesses Can Benefit from Greywater System Water Reuse

At a time of increasing water scarcity, rising costs and rapidly evolving sustainability goals, innovative strategies may be necessary to keep bills down, meet environmental targets and protect the environment. 

Reusing your water is a potential solution to this. “Greywater” is the water that your business pours away every single day. It’s a literal drain on your business, and it can be reused to your advantage. Thinking more smartly about how you use it could bring significant benefits to your business. 

What is Greywater?

Greywater is lightly used household wastewater that excludes toilet waste and can often be reused for non-drinking purposes, such as irrigation or flushing. It typically comes from sinks, showers, and washing machines, making it safer and easier to treat other types of wastewater.

More specifically, the term refers to domestic wastewater that has not come into contact with human waste. It originates from sources such as bathroom sinks, showers, bathtubs, and washing machines and may contain traces of soap, dirt, or food particles. 

What’s the Difference Between Greywater and Wastewater?

Unlike “wastewater” (water from toilets and the like, which needs specialist treatment), greywater has lower levels of pathogens and organic matter, making it suitable for reuse in landscape irrigation, toilet flushing or other non-potable applications when properly treated. Reusing greywater helps conserve freshwater and reduce strain on sewage systems, especially in water-scarce regions.

Can Businesses in the UK Legally Use Greywater?

Yes, businesses in the UK can legally use greywater, provided they comply with specific regulations and safety standards. Greywater reuse is permitted for non-potable applications such as toilet flushing and irrigation, so long as the systems are properly designed, maintained and do not pose a risk to public health or the environment.

UK businesses must follow the guidance in the Ministry of Housing’s Approved Document H and may need to obtain environmental permits for discharge. Greywater must not come into contact with edible crops or generate aerosols indoors. Proper filtration, signage and backflow prevention are essential for legal compliance.

How Do Greywater Systems Work?

Greywater systems collect and redirect lightly used household water, typically from sinks, showers and washing machines, for reuse in irrigation or toilet flushing. These systems filter and sometimes treat the water before distributing it through dedicated plumbing, reducing water demand and easing pressure on our sewage infrastructure. 

Greywater Drainage and Collection Systems

Greywater drainage systems separate wastewater from sinks, showers, and washing machines into dedicated pipes that bypass the sewer. These pipes flow directly to a surge tank, which temporarily stores the water and regulates output. Tanks vary in size and material, often including sediment traps to remove solids. Filtration typically involves mesh screens, sand filters, or biofilters to remove debris, soap and organic matter. 

Advanced systems may use UV or chemical disinfection for reuse in toilet flushing or subsurface irrigation. Gravity-fed designs are simpler and energy-efficient, while pumped systems offer greater layout flexibility. Proper slope, venting and backflow prevention are essential to avoid contamination and ensure smooth drainage. 

Greywater Treatment and Recycling Systems

But filtering isn’t the only way in which greywater can be treated. 

Mechanical treatment removes solids through filtration, screens or sedimentation. Biological treatment uses microbes to break down organic matter in biofilters or constructed wetlands. 

Chemical treatment involves disinfectants such as chlorine or ozone to kill pathogens and neutralise contaminants. These methods can be used individually or combined, depending on what you’re reusing it for. Irrigation may, for example, only need mechanical and biological steps, while toilet reuse will require chemical disinfection.

What can Greywater be Used for?

Greywater can be used for non-potable applications such as landscape irrigation, toilet flushing, and cooling systems. It’s ideal for subsurface irrigation, especially for ornamental plants and lawns. It can also be reused for toilet flushing, industrial processes, or vehicle washing. But all of this is subject to the extremely important caveat that it’s properly filtered and treated to avoid health risks.

Business Benefits of Greywater Recycling Systems in the UK

Greywater recycling systems offer UK businesses a strategic advantage by cutting costs, enhancing sustainability and improving water quality while aligning with future regulations. Business sectors including hospitality, education and commercial real estate are already seeing measurable returns.

Cost Savings on Water Bills

Greywater systems can reduce water consumption by up to 50% in commercial buildings. The University of Manchester, for example, saves 4.5 million litres annually through greywater harvesting and reuse.

Sustainability and Environmental Responsibility

Reusing greywater lowers both water and carbon footprints. It reduces reliance on mains water and decreases wastewater discharge, helping support the UK’s broader climate and water-efficiency goals. Hotels using greywater systems can showcase real-time savings to guests, turning sustainability into a brand asset. 

Meeting ESG and CSR Goals

Greywater recycling supports Environmental, Social, and Governance (ESG) and Corporate Social Responsibility (CSR) targets. It demonstrates proactive resource management and environmental stewardship—key metrics for investors, regulators, and eco-conscious clients.

Future-Proofing Against Water Scarcity and Regulation

With the UK facing a projected 4,800 megalitres per day water shortfall by 2050, greywater systems help businesses stay ahead of tightening regulations and resource constraints. 

Greywater Treatment System Costs for Businesses

In the UK, greywater treatment systems for businesses typically cost between £3,000–£10,000 for small commercial setups and £25,000–£100,000+ for large-scale systems, depending on complexity, treatment level and building type. Installation is the major upfront expense, while maintenance remains relatively low and predictable.

Factors Affecting Greywater System Cost

Greywater system costs vary widely depending on property size, water output, and treatment type. Such factors can influence installation complexity, equipment needs and long-term maintenance.

Larger buildings require more extensive plumbing modifications, larger tanks, and higher-capacity pumps. A small café might need a basic gravity-fed system, while a hotel or university campus would require multi-zone setups with automated controls.

The daily volume of greywater affects tank size, filtration speed, and reuse potential. High-output sites like laundries or gyms need robust systems to handle continuous flow, while low-output sites may use simpler, batch-based designs.

There are three main types of treatment for greywater:

• Mechanical: Basic filtration (screens, sediment traps) is low-cost and suitable for irrigation.

• Biological: Biofilters or wetlands add complexity and space requirements but improve water quality.

• Chemical: UV or chlorine disinfection increases upfront and maintenance costs but enables indoor reuse, such as toilet flushing.

Other factors can also affect cost. Automated systems with sensors and smart controls cost more but offer better efficiency and monitoring. Manual systems are cheaper but require more user oversight. And regulatory compliance also comes at a cost. It may rise due to backflow prevention, signage and water quality testing, especially for systems used indoors or in public buildings.

Greywater System Options for UK Businesses

Depending on building type, water output, and reuse needs, businesses can choose from several system designs tailored to their scale and operations.

Greywater Harvesting Systems vs Rainwater Harvesting

Greywater harvesting captures lightly used water from sinks, showers and washing machines, while rainwater harvesting collects precipitation from rooftops. Greywater is generated daily and requires filtration before reuse; rainwater is seasonal and often cleaner, but less predictable.

Onsite Greywater Reuse Systems

These systems treat and reuse greywater directly within the building for non-potable uses such as toilet flushing, landscape irrigation or cooling. Common in hotels, gyms, and offices, they include filtration units, tanks and pumps. 

Centralised Greywater Recycling Systems

Designed for large complexes such as universities, industrial parks, or multi-building developments, these systems collect greywater from multiple sources, treat it centrally, and redistribute it for reuse. They offer economies of scale, advanced treatment options and integration with broader water management infrastructure.

Greywater and UK Regulations

UK greywater systems have to comply with building regulations, water quality standards, and health & safety protocols to ensure safe reuse and legal operation. Businesses must follow specific design, installation, and maintenance rules.

Greywater reuse is governed by Approved Document G of the Building Regulations 2010, which sets water efficiency and sanitation standards. Systems must also meet BS 8525-1:2010, the British Standard for greywater design, treatment, and risk assessment.

Water must not be connected to the mains supply and must be clearly labelled to avoid cross-contamination. The Water Supply (Water Quality) Regulations 2016 outline acceptable water quality for reuse, especially for toilet flushing or irrigation. 

Health & safety concerns include preventing aerosol formation, ensuring backflow protection and conducting regular maintenance. 

Common Uses of Greywater in Business Settings

Here are some common ways greywater can be used in a business environment. You might be surprised by how varied they can be!

Irrigation for Landscaping (Office complexes, Retail Parks, etc)

Greywater is ideal for irrigating ornamental plants, lawns, and green spaces in commercial environments. Offices and retail parks often use subsurface irrigation systems to avoid public contact and meet health standards. 

Toilet Flushing in Commercial Properties

Toilet flushing is one of the most common greywater applications in hotels, gyms, and office buildings. Treated greywater is stored in dedicated tanks and pumped to cisterns, cutting potable water use by up to 30%. Such systems must include backflow prevention and clear signage.

Cooling Systems in Industrial Settings

In factories and data centres, greywater can supplement cooling towers or HVAC systems. While it requires higher filtration to prevent scaling or corrosion, because of the high volume of water that would otherwise be required, this reuse can help to lower demand on freshwater supplies and support operational resilience during droughts or restrictions.

Cleaning Processes

Some businesses, such as vehicle depots or warehouses, use greywater for external cleaning tasks such as floor washing or equipment rinsing. This is suitable when water quality demands are low and systems are designed to prevent aerosol formation or surface runoff.

By reducing your business's carbon footprint, you consume less treated water, helping mitigate the UK’s growing water scarcity problem and lowering both your business's water rates and the environmental impact of the water industry. The benefits of reusing greywater are clear. Start by creating a water plan for your business, and then you can look at which system will work best for you.