NAV Adoption Arrangements for Developments

What Is a NAV?

A New Appointment and Variation (NAV) is a water and, in many cases, wastewater company appointed by Ofwat to serve a specific geographic area, known as an inset, instead of the regional incumbent water company. A NAV is a fully regulated water provider in its own right, with the same duties, responsibilities and quality standards as any incumbent under the Water Industry Act 1991. Residents on a NAV site get the same protected, regulated service, so a NAV never means a compromise on water quality or standards.

The NAV market has grown sharply. It went from around 70 sites in 2017 to well over 2,000 by late 2025, because developers have recognised the commercial and service advantages on the right schemes. There are currently around a dozen licensed NAV operators in the UK.

How a NAV Works

Once appointed to your site, a NAV owns and maintains the water and wastewater network within the development. It sources water in one of two ways: from its own supply, or, more commonly, by buying it wholesale from the regional incumbent under a bulk supply agreement, with a bulk meter installed at the site boundary. The incumbent provides the water at the boundary; the NAV distributes it within the site and bills the residents. In practice this means:

• The NAV becomes the appointed water and wastewater provider for the inset area
• Water is delivered to the site boundary under a bulk supply agreement
• The NAV owns and operates the on-site network
• Residents are billed by the NAV, at prices regulated to be no worse than the incumbent's

Why Developers Choose a NAV

The NAV route can offer real advantages on the right development:

• Asset value. Because a NAV owns the water network, the value of those assets can be returned to the developer, rather than the network simply being adopted by the incumbent for nothing.
• A single relationship on larger sites. A NAV can provide both water and wastewater for the inset, simplifying the arrangement.
• Competitive service. NAVs compete on service levels and responsiveness, and are regulated to the same standards as incumbents.
• Coordinated with self-lay. The NAV route works alongside self-lay construction, so the same coordinated approach that builds the network also sets up its long-term ownership.

The trade-off is that a NAV involves an appointment process with Ofwat and only makes sense above a certain scale, which is why the route needs assessing project by project rather than assuming it always applies.

NAV, Self-Lay or Incumbent: Which Route?

There is more than one way to get water onto a development and decide who owns it long term. The right choice depends on the size and commercial profile of the scheme.

As a WIRS accredited self-lay provider that also arranges NAV adoption, Air Utilities can advise on and deliver whichever route gives you the best commercial and programme outcome, rather than pushing a single option.

How We Help With NAV Adoption

• Route assessment, comparing NAV, self-lay and incumbent adoption for your specific scheme
• NAV partner introduction and coordination, so the right NAV operator is appointed for your site
• Self-lay construction of the water network to WIRS adoptable standards
• Bulk supply and point of connection coordination with the incumbent
• Integration with your wider utilities, so water sits within a coordinated multi-utility programme

Because Air Utilities builds the water network as a WIRS accredited self-lay provider and arranges the NAV adoption through partners, the construction and the long-term ownership are planned together, not bolted on separately.

How Long Does a NAV Arrangement Take?

A NAV involves a formal appointment or variation by Ofwat, so it carries its own lead time on top of the physical connection, and it is a decision to make early in a scheme rather than late. As a general guide the appointment process runs alongside the site's design and construction programme, which is why the route should be assessed at the planning stage, so the appointment is progressing in the background while the network is being designed and built. We flag whether a NAV suits your scheme at the earliest opportunity so it never becomes a late-stage bottleneck.

Our NAV Adoption Process

1. 1

   Route assessment

   We evaluate whether a NAV, self-lay or incumbent route best suits your development commercially and operationally.

2. 2

   NAV partner and appointment

   Where a NAV fits, we coordinate the right NAV operator, who applies to Ofwat for the appointment or variation.

3. 3

   Design and bulk supply

   We design the on-site network and coordinate the bulk supply agreement and point of connection with the incumbent.

4. 4

   Self-lay construction

   Our WIRS accredited teams build the water network to adoptable standards.

5. 5

   Adoption and handover

   The NAV adopts and takes ownership of the completed network, and residents are onboarded to the NAV.

Frequently Asked Questions