Castle Water

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Our expert guide to Castle Water for businesses

Castle Water is one of Britain’s largest independent business water retailers, supplying over 250,000 commercial properties across England and Scotland.

Castle Water became the default supplier for businesses in the Thames Water region following the water market deregulation. If your business hasn’t switched water suppliers, there’s a good chance Castle Water currently manages your account.

Sticking with the default supplier is simple, but often not the cheapest option. Businesses that actively choose their water retailer can often unlock better deals, tailored tariffs, and improved service.

Check how much your business could save by entering your postcode above.

Castle Water customer service

Here’s how to reach Castle Water’s business support team:

Castle Water contact number

You can call Castle Water on 01250 718 700. Phone lines are open Monday to Friday, 8am – 5pm.

Castle Water login

Castle Water customers can manage their account online via the ‘Customer Portal’. You can view bills, update details, submit meter readings, and track your water usage.

Castle Water email

Business water customers can email customer services at customerservices@castlewater.co.uk for support, complaints, or general enquiries.

Castle Water prices

Castle Water is the default water retailer for businesses in several regions, including Thames Water, Affinity Water (Central, East, and South East), South East Water (East and West), and Portsmouth Water.

Below are the current default business water rates for small commercial properties in these areas if you haven’t signed a fixed tariff with Castle Water.

💡 Castle Water also offers fixed-price contracts across England and Scotland. These fixed rates are not published online and are available on request.

Thames Water default prices

Standing water: £67.52
Volumetric water: £2.5895/m³
Standing wastewater: £139.23
Volumetric wastewater: £1.7054/m³

Affinity Water default prices

Central region

Standing water: £89.37
Volumetric water: £1.4417/m³

East region

Standing water: £89.37
Volumetric water: £2.4036/m³

South East region

Standing water: £89.37
Volumetric water: £2.4036/m³

South East Water default prices

East region

Standing water: £77.56
Volumetric water: £2.8903/m³

West region

Standing water: £77.56
Volumetric water: £2.9826/m³

Portsmouth Water default prices

Standing water: £78.93
Volumetric water: 0.9119/m³

💡Default charges in Portsmouth will increase from 1 July 2025.

Castle Water acquisitions and regional coverage

While Castle Water is best known as the default supplier for the Thames Water region, it has expanded significantly through acquisitions over recent years.

Castle Water took over the non-household customer bases of Affinity Water, South East Water, and Portsmouth Water, making it the default retailer for businesses in those areas as well.

In January 2025 Castle Water also acquired Brightwater, further expanding its portfolio of business customers and reinforcing its position as a major player in Britain’s commercial water market. The Brightwater acquisition added thousands of additional business sites to Castle Water’s growing customer base.

Castle Water tariffs

Castle Water provides a range of tariff types to suit different business needs, from basic standard rates to fixed-term deals with added benefits.

Default contract

Businesses that haven’t actively chosen a tariff are placed on a default business water tariff. While convenient, this option is often more expensive than a fixed contract. You can switch to a better deal at any time to help lower your water costs.

Fixed contract

A fixed contract gives you a set retail fee for the length of the agreement. This can make budgeting easier and is typically cheaper than default pricing. You still have the flexibility to review your options when your contract ends.

Castle Water contract features

Castle Water fixed contracts come with key terms that help businesses manage payments, avoid surprises, and stay in control of their water account.

Payment methods

Castle Water typically requires Direct Debit for all payments on fixed contracts. Charges are collected around 14 days after each bill is issued. If a Direct Debit is cancelled or fails, any available discounts may be removed.

No advance payments

With Castle Water’s monthly in arrears billing, you don’t pay for water in advance. This helps with cash flow and gives you greater control over your monthly outgoings.

End of contract

You’ll receive a renewal notice at least 30 days before your fixed-term contract ends. If no new agreement is signed, your account will move to default rates, which may be higher.

Credit checks and deposits

Castle Water may carry out credit checks at the start or during the life of the contract. Some businesses may be asked to pay a security deposit, which can be used to settle any outstanding charges if necessary.

How to get a Castle Water quote

At AquaSwitch, we specialise in helping companies compare business water suppliers and find the best deals. If you’re looking to compare Castle Water with other business water suppliers, our simple three-step process makes it easy to switch and save.

Enter your postcode

Start by entering your business postcode above and a few simple details about your business.

Compare prices

Review quotes from Castle Water and other business water suppliers to find the best rates and contract terms for your needs.

Switch and save

Once you’ve found the right deal, you can switch business water suppliers quickly and easily, ensuring you get competitive rates and the right service for your business.

Castle Water additional services

Castle Water provides a range of services designed to help businesses cut water waste, reduce costs, and maintain operational resilience. Whether you’re a small office or a large industrial site, their team offers practical support tailored to your needs.

Water audit

Castle Water offers professional water audits to help businesses better understand their usage and identify opportunities to reduce water consumption. These audits often uncover inefficiencies or commercial water leaks that have gone unnoticed. Most businesses see water savings of 5% to 8%, with some saving significantly more, depending on their operations.

Contingency planning

If water supply is critical to your business, Castle Water can help you develop a robust water contingency plan. This ensures you remain operational during unexpected water supply interruptions and helps protect your revenue and customer service levels during any disruption.

Smart water meters

Installing smart water meter gives businesses greater visibility over their consumption. Castle Water uses real-time data to identify unusual usage patterns, potential leaks, or operational inefficiencies, helping you take quick, informed action and keep bills under control.

New connections

Castle Water supports businesses with new water connections, managing everything from planning and applications to coordinating with the local water company. This saves time, cuts down on admin, and helps ensure your site is connected with minimal hassle.

Trade effluent management

Castle Water is a leading expert in trade effluent services. Castle Water provides end-to-end support if your business discharges wastewater as part of its processes, such as food production, manufacturing, or chemical treatment. Their team can handle consent applications, ensure ongoing compliance, monitor discharge volumes, and help you manage trade effluent charges.

Castle Water customer reviews

Castle Water has an excellent Trustpilot rating of 4.6, based on reviews from business customers. Below are some common themes highlighted in verified reviews:

Pros

Straightforward setup: Many customers say the onboarding process is quick and hassle-free.
Competitive rates: Several businesses highlight good value and savings compared to previous suppliers.
Clear online portal: The ‘Customer Portal’ is praised for making it easy to view bills, submit readings, and manage usage.

Cons

Billing accuracy: Some customers report occasional issues with incorrect bills or delayed adjustments.
Customer support delays: While many find support helpful, there are some reports of slow response times when dealing with complex queries.
Contract renewals: A few reviewers mention frustration about being moved to higher rates when they miss renewal deadlines.