Water Supply Assessment
Ensuring adequate water supply is a critical consideration for any new development. A Water Supply Assessment demonstrates that there is sufficient clean water available to serve the proposed development without compromising supply to existing properties. With increasing pressure on water resources across much of England, particularly in the south and east, planning authorities are placing growing emphasis on water supply matters.
Typical Cost
£300 – £5,000+
Turnaround
1 – 6 weeks
AI Report
Minutes
Generate your Water Supply Assessment with AI
Skip the weeks of waiting. Get a professional draft in minutes.
What is a Water Supply Assessment?
A Water Supply Assessment evaluates whether the existing water supply infrastructure can accommodate the additional demand generated by a proposed development. It considers the capacity of local water mains, the pressure and flow rates available at the point of connection, and any upgrades or reinforcement works that may be needed. The assessment also addresses water efficiency measures that can reduce the overall demand of the development, which is particularly important in areas designated as zones of serious water stress by the Environment Agency.
When is a Water Supply Assessment required?
Local planning authorities typically require a Water Supply Assessment for major residential developments of 10 or more dwellings, large commercial or industrial schemes with significant water demand, and any development in an area where the water company has identified supply constraints. The requirement is often triggered by consultation responses from the statutory water company, which is consulted on most major applications. Under Section 45 of the Water Industry Act 1991, water companies have a duty to provide a supply of wholesome water, but they are entitled to require infrastructure upgrades at the developer's expense where existing capacity is insufficient.
What does a Water Supply Assessment include?
A comprehensive Water Supply Assessment includes an estimate of the total daily water demand of the proposed development based on occupancy rates and per capita consumption figures, an analysis of the existing supply infrastructure including main sizes and pressures, confirmation from the water company regarding available capacity, details of any reinforcement or diversion works needed, proposals for water efficiency measures including fixtures and fittings specifications, and consideration of fire hydrant requirements in consultation with the local fire and rescue service.
How much does a Water Supply Assessment cost?
A basic Water Supply Assessment for a minor residential scheme typically costs between £400 and £1,000. For major developments requiring detailed demand calculations, infrastructure modelling, and liaison with the water company, costs generally range from £1,500 to £4,000. Very large developments that necessitate significant network modelling or strategic infrastructure upgrades may involve assessment costs of £5,000 to £10,000, though such schemes often negotiate the assessment as part of wider infrastructure planning agreements.
Who can prepare a Water Supply Assessment?
Water Supply Assessments are prepared by civil engineers, utilities consultants, or specialist water infrastructure consultants. The assessment often requires close liaison with the relevant water company, and many consultants have established working relationships with the major water companies operating in England and Wales. Membership of the Chartered Institution of Water and Environmental Management or registration as a Chartered Engineer with ICE adds credibility to the assessment.
How long does a Water Supply Assessment take?
The timeline depends heavily on the responsiveness of the local water company. A straightforward assessment where capacity is available can be completed in 2 to 3 weeks. Assessments requiring the water company to carry out network modelling or capacity studies typically take 6 to 12 weeks. In areas with known supply constraints, the process can extend further where strategic infrastructure solutions are being developed.
Frequently Asked Questions
Is a Water Supply Assessment the same as a water connection application?
No. A Water Supply Assessment is a planning document that demonstrates adequate water supply can be provided. A water connection application is a separate request made to the water company to physically connect your development to the water mains. The assessment supports your planning application, while the connection application is typically made after planning permission is secured.
Who provides the water supply information?
The relevant statutory water company provides information on existing infrastructure capacity, main sizes, pressures, and any planned reinforcement works. In England, water companies include Thames Water, Severn Trent, United Utilities, Anglian Water, and others depending on the region. Your consultant will liaise with the appropriate company to obtain the technical data needed for the assessment.
What water efficiency standards apply to new developments?
Building Regulations Part G sets a mandatory water efficiency standard of 125 litres per person per day for new dwellings. However, local planning policies in many water-stressed areas require a tighter standard of 110 litres per person per day, which is the optional higher standard permitted under Building Regulations. Your Water Supply Assessment should confirm which standard applies and how the development will achieve it through specification of efficient fixtures and fittings.
Can a water company refuse to supply a new development?
Water companies have a statutory duty to supply water under the Water Industry Act 1991 and cannot simply refuse a connection. However, they can require the developer to fund infrastructure reinforcement where existing capacity is insufficient. In practice, this means the developer pays for upsizing mains, installing booster pumps, or extending the network to serve the development. These costs can be substantial for large schemes.
Do I need a Water Supply Assessment for a householder extension?
No. Water Supply Assessments are not required for householder extensions or minor alterations that do not significantly increase water demand. The existing water supply to your property will be sufficient for an extension. A Water Supply Assessment only becomes relevant when a development creates materially increased demand, such as new dwellings or commercial premises.
What areas of England are water stressed?
The Environment Agency classifies areas of England according to their level of water stress. Much of southern and eastern England is classified as an area of serious water stress, including London, the Thames Valley, East Anglia, and parts of the south east. Water companies in these regions are more likely to impose the tighter 110 litres per person per day standard and may scrutinise water supply capacity more carefully.
Does a Water Supply Assessment cover fire hydrants?
A thorough assessment should address fire hydrant provision. The local fire and rescue service may require new fire hydrants to be installed as part of the development, particularly for residential estates and commercial schemes. The water supply needs to provide adequate flow and pressure to serve hydrants, and this demand is factored into the overall capacity assessment. Requirements are typically set out in consultation with the fire authority during the planning process.
What happens if water pressure is too low for my development?
If the existing water pressure is insufficient to serve the proposed development, the water company may need to install booster pumping stations or upsize existing water mains to increase pressure and flow. The cost of these works is borne by the developer. Alternatively, the development may need to incorporate its own on-site boosting system, which is common for taller buildings where pressure at upper floors is a concern.
Can rainwater harvesting reduce the need for mains water supply?
Rainwater harvesting systems can reduce mains water demand by collecting and treating rainwater for non-potable uses such as toilet flushing, laundry, and garden irrigation. While these systems are encouraged in sustainability policies, they cannot fully replace mains water supply as they are unreliable during dry periods. A Water Supply Assessment should acknowledge any rainwater harvesting proposals but must still demonstrate adequate mains supply capacity.
How does a Water Supply Assessment relate to the drainage strategy?
The Water Supply Assessment and drainage strategy are complementary documents. The water supply side deals with clean water coming into the development, while the drainage strategy addresses how foul water and surface water leave the site. Together they provide a complete picture of the water cycle for the development. Planning authorities increasingly expect applicants to consider both elements together to ensure a coherent and sustainable approach to water management.