A shop, café or takeaway downstairs with a flat upstairs is a familiar setup for small business owners and landlords. What is less obvious is that the two units may share a single water supply. Wave Utilities, a water retailer, notes that a business in an older property that has been converted or split, such as a takeaway or shop with a flat above, could be on a shared supply, and that you might only find out when your bill shows water use you cannot account for.
Here is why one supply causes problems in a mixed-use building, how it affects the way the water is billed, and what splitting it actually involves.
Why one supply causes problems
One supply means one bill. Wave explains that this typically goes to only one of the customers, so a business sharing with a household can end up paying for the household’s water as well as its own.
Fitting a sub-meter helps you see what each unit uses, but it does not split the bill. In Wave’s words, the bill you receive will still reflect the whole property’s water use, so the occupiers still have to agree how to divide it between themselves.
Then there is access to the water itself. The Water Fittings Regulations require each pipe supplying separate premises to have a stopvalve that can shut off that supply without shutting off the supply to any other premises. Fittings lawfully installed before 1 July 1999 do not have to be changed to meet this, so an older building may not have one. If it does not, turning off the water for a repair in the flat can mean turning it off in the shop too.
How the water is billed
Since April 2017, water services to business premises have been split into wholesale and retail. The wholesaler, such as Thames Water, treats and transports the water, while a retailer issues the bills and handles queries. All non-household customers are able to switch retailer, and that includes shops.
The question for a mixed-use building is which side of that line it falls on. Ofwat’s eligibility guidance covers this exact case: where a shop and household form part of the same premises and share a supply point, the premises are treated as mixed-use, and whether they belong in the business market depends on their principal use. The same guidance says premises liable for both council tax and business rates will normally be classified as non-household, unless there are grounds to think their principal use is as a home.
In other words, while the shop and flat share a supply, the building is assessed as one premises and classed by its main use. Separate supplies change that. Ofwat’s guidance gives the example of living accommodation on a separate supply being classified as household rather than business. With a supply each, each unit can be assessed on its own use, and the shop can hold its own business account with a retailer of its choice.
What the water company needs from you
The first step is an application to the wholesaler, not the retailer. Wave advises businesses that want their own supply to contact their wholesaler’s new developments team. Each water company runs its own process, and some details differ. Affinity Water, for example, states that if the new connection is for non-household premises, a retailer must be selected, so it helps to have that decided before you apply.
In London, Thames Water says it will send a quote within 28 days, covering the work between the property boundary and its main. Inside the building, the pipework for each unit needs separating so that each runs from its own supply. Thames asks for the new supply pipe to pass a water regulations inspection or be certified by a WaterSafe approved plumber.
What the dig involves on a high street
The new connection runs from the water main to the building, so if the main is under the road or pavement outside, the footway has to be opened up.
That needs a permit. Almost every highway authority in England now operates a permit scheme, and the statutory guidance sets minimum notice periods: at least three working days for works lasting three working days or less, and at least ten working days for works lasting four to ten working days. Whoever carries out the street work has to plan around that notice.
Where the connection is made also shapes the cost. Water companies price connections by the surface that has to be opened, and Thames Water’s 2026/27 charging arrangements charge less for a connection made in a footpath than in a road, with pipe laying charged per metre on top. Thames aims to complete a connection within four months of agreeing the work with the local authority or Transport for London, and says it can take longer where traffic management is difficult or extensive.
Once the work is finished, the footway has to be put back to the standard set by the Specification for the Reinstatement of Openings in Highways, which has been statutory guidance since 10 May 2021.
For a shop, the practical issue is timing. A trench outside the front door during trading hours costs you custom, so it is worth agreeing working times, and how the entrance will stay open, before the work is booked.
Who can do the work in the street
The connection does not have to be built by the water company. Ofwat describes self-lay as choosing your own contractor to do the work, and Thames Water’s charging arrangements treat connections up to 63 mm as contestable, meaning an accredited contractor can carry them out. Thames says a typical home needs a 25 mm or 32 mm connection, well inside that limit.
Before you approach anyone, check they are accredited under the Water Industry Registration Scheme on the LRQA WIRS register. For a shop, the practical appeal of an accredited contractor is having one firm deal with the footway, the permit and the reinstatement, and plan the dig around trading hours. McFadden Utilities, a WIRS-accredited self-lay provider in Welwyn Garden City that has been family-run since 1980, is one firm that takes on single service connections like this, working from the water company’s design through to the live connection and making good the pavement afterwards. The water company still checks the work and adopts the new pipework once complete, so the choice comes down to comparing its price with an accredited contractor’s price for the same job.
The short version
A shop and flat on one supply is not unusual, and it is fixable. While they share it, there is one bill, one point of failure, and Ofwat’s guidance treats the building as a single mixed-use premises. Separating the supply gives each unit its own bill and its own way to turn the water off. Settle the retailer question early, apply to the wholesaler, and plan the footway work around your trading hours.
