Are You Eligible for a Surface Water Drainage Refund?

Surface water drainage is a standard charge on most business water bills in the UK, but not every site is liable for these costs. Over time, changes to your premises or billing errors may mean your business could be eligible for a surface water drainage refund. Understanding this complex area can help you check whether your business is paying the correct amount, and whether there may be grounds to review past charges.

What Is Surface Water Drainage?

Surface water drainage refers to the removal of rainwater from roofs, car parks, and other hard surfaces on your premises, which is then transferred to the public sewer system. Water companies charge businesses for this service because it places demands on sewerage infrastructure. The fee is usually listed separately from other wastewater charges on your bill.

Who Pays for Surface Water Drainage?

Most commercial properties in England, Scotland and Wales are billed for surface water drainage, unless it can be proven that none of the rainwater from the property enters the public sewer. The charge is typically based on property size, rateable value, or a banding system set by your water retailer or wholesaler.

There are scenarios where your business may not be responsible for these charges:

• No surface water from the site drains to the public sewer (for example, all water soaks away naturally or is collected for reuse).
• Part of the property has been redeveloped, and drainage arrangements have changed.
• Historic billing errors have resulted in charges for services not received.

Eligibility for a Surface Water Drainage Refund

If your business property does not, or no longer, drains surface water to the public sewer, you could be eligible for a refund of past charges. Eligibility depends on several factors:

• Drainage arrangements: If your site drains to a soakaway, watercourse, or a private system instead of the public sewer, you may not be liable for these charges.
• Billing period: Water companies may only refund charges for a set period, often up to six years, but this varies and is subject to the retailer’s terms and local policies.
• Evidence: You will usually need to provide site plans or photographs showing that surface water does not enter public sewers.

For more information, you can refer to the guidance from Consumer Council for Water and Ofwat, the industry regulator.

How to Check Your Surface Water Drainage Charges

To determine if you may have been incorrectly charged, start by reviewing your most recent water bills. Look for a line item called ‘surface water drainage’, ‘SWD’, or something similar. Pay attention to:

• The basis of the charge (banded, rateable value, or site area).
• The property address and description – check for errors or outdated details.
• Whether you have recently made changes to your drainage or building layout.

Having trouble interpreting your bill? Our business water bill audit service could help clarify your charges and spot possible overpayments.

Common Reasons for Surface Water Drainage Overcharges

• Incorrect property details: Billing based on outdated or incorrect information about your site’s drainage.
• Redevelopment: Changes to your building or car park that alter drainage patterns not reflected in your bill.
• Shared sites: Multi-occupancy sites sometimes face errors in how charges are split or allocated.
• Metering errors: Confusion over which parts of the site are connected to the public sewer.

These issues can be particularly common for older buildings, large sites, or businesses occupying part of a bigger commercial complex.

Steps to Review and Challenge Surface Water Drainage Charges

1. Gather your water bills (ideally for the past 12 months).
2. Check your property’s drainage arrangements – ask your facilities or maintenance team if unsure.
3. Compare your charges with the current site set-up. Look for discrepancies.
4. If you believe your charges are incorrect, contact your water retailer. Provide supporting evidence such as site plans or photographs.
5. Request clarification in writing on how your charges have been calculated.

For a step-by-step guide, see how our review works or explore more on surface water drainage charges.

How Far Back Can Refunds Go?

The period for which you could receive a refund (if eligible) varies by water company and is subject to their policies. In England, some refunds may be backdated several years, but there is often a limit. In Scotland and Wales, rules may differ. Always check with your retailer for their specific policies and keep copies of all correspondence.

Switching Water Retailers vs. Challenging Charges

It’s important to distinguish between switching suppliers and correcting billing errors. In England, most businesses can choose their water retailer, but the underlying drainage charges are typically set by the wholesaler and will follow you to any new retailer. In Scotland, water is supplied through a licensed market, while in Wales only very large users can switch. Therefore, reviewing current and historic charges is a separate process from changing supplier. Learn more about business water savings and what to consider before switching.

What Evidence Is Needed for a Surface Water Drainage Review?

To support a challenge or refund request, you may need to provide:

• Site layout plans showing drainage routes
• Photographs of drains, soakaways, or areas that do not connect to public sewers
• Planning or construction documents if recent changes were made
• Letters or reports from building managers or drainage specialists

Water retailers are likely to request a site visit or further investigation if the evidence is unclear.

How Can a Professional Water Bill Audit Help?

For many businesses, especially those managing multiple sites or complex properties, a professional water bill audit could help identify surface water drainage overcharges. Auditors review historical bills, check your site’s drainage arrangements, and provide a plain-English summary of potential issues. This may help your business secure a more accurate bill going forward and highlight areas for possible challenge. Find out more on our business water bill audit page or upload your water bills for review.

Further Resources

• Open Water: Guidance on the business water market in England
• GOV.UK: Information on business rates and property drainage
• frequently asked questions about business water bills

Frequently asked questions

Updated 28 October 2026. This guide is general information, not legal or financial advice. Charges and rules vary by water company and nation.