Water efficiency and viability in new build homes

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Climate change, population pressures and an aging infrastructure are placing increasing strain on our water supply – the recent hot, dry summer being a case in point. As individual households negotiate a hosepipe ban, many councils are considering introducing policies to restrict water usage in new homes and thereby reduce local pressures on supply.

Current Building Regulations (Part G) place a 125 litres per person per day (l/p/d) water use restriction on new homes with an option for local authorities to specify a higher standard of 110 l/p/d through local plan policy. Indeed many have taken the latter option and most authorities we work with at Three Dragons have or are developing policies to adopt this standard.

From a viability perspective the cost of achieving 110 l/p/d is de minimus, achieved through simple changes to fittings. In its 2024 report, Wat Er Save, the HBF notes both the financial savings to households of living in a water efficient home (average saving of £126 per year where 110l/p/d is achieved) and to the nation, estimating the measure could have saved almost 8.5 billion litres of water in 2023 alone, “equivalent of 3,360 Olympic-sized swimming pools”.

Going beyond this the NPPF August 2026 allows for standards above 110l/p/d, “exceptionally …… in areas of serious water stress” (PM13, 1, b, ii). Water companies also have been encouraging such an approach (e.g. Shared Standards in Water Efficiency for Local Plans June 2025 covers a significant area in Eastern England, an area with low rainfall but high housing growth. Through the Shared Standards authorities are recommended to adopt policy requirements in new Local Plans “of up to 85 litres/person/day (l/p/d) for residential developments”.

Some authorities are already acting, examples include

The Regulation 19 draft Greater Cambridge Local Plan requires “for residential development of 100 or more dwellings, water usage of no more than 80 litres/person/day … For residential development of less than 100 dwellings, water usage of 90 litres/person/day” (draft Policy CC/WE)

The Regulation 19 draft Broads Authority Local Plan requires water usage of 90l/p/d (draft policy PUBDM7 main modifications)

The Regulation 19 draft Milton Keynes City Plan requires “proposals for residential development to achieve….. a 93 litres per person per day water efficiency standard for mains supplied water/potable water” draft Policy CEA5)

Crawley Boro Council has an adopted (October 2024) Strategic Policy SDC4: Water Neutrality -requiring new residential development within the part of the Borough that is ‘water stressed’ to be designed to utilise no more than 85 litres of mains supplied water per person per day.

Although such policies will impact on development viability, the cost need not be prohibitive. The HBF Water Ready report 2024 demonstrates how a fittings first approach can be utilised to achieve a significant proportion of the proposed higher standards and that this will be further improved as the production of new technologies increases. Whilst Greater Cambridge acknowledges that achieving 80l/p/d will require “some form of water reuse or recycling”, the viability impact for this could be around £6,000 per dwelling (Water reuse in new housing CIWEM 2024). However, where a fittings based approach can achieve the standard of 90 or even 85 l/p/d the costs could be significantly lower – ranging from c£500 to £3,000 per dwelling dependent upon which technologies are employed. (See Water Ready Report 2024 HBF).

Tags: Development Viability, Tackling Climate Change