CIH briefing on DEFRA’s consultation on updating Part G of the building regulations on water efficiency in new homes

The government has set a target of building 1.5 million new homes in this parliament. Water scarcity is one barrier to achieving this, especially in parts of the country where drought and water management issues are common, like Cambridge. There are documented cases of water scarcity and capacity issues slowing or stopping new housing developments entirely.

On the supply side, government has committed to building new reservoirs to tackle this. On the demand side, government is consulting on updates to Part G of the Building Regulations to reduce the average water demand per home. CIH is responding to the consultation and has prepared this briefing to support our members to understand the proposed changes. 

We welcome feedback on any of the issues raised in this briefing. At the end of this briefing, we have listed the main questions we would be interested in hearing from CIH members on. Feedback we receive will inform our consultation response. Please email policyandpractice@cih.org by 3 December 2025. 

The consultation can be found here. The deadline for responding to the consultation is 16 December 2025. 

Part G of the Building Regulations currently sets a minimum Water Efficiency Standard of 125 litres per day (l/p/d). It also includes an optional technical standard, already adopted by several Local Planning Authorities (LPAs), of 110 l/p/d, which is intended to be used in areas of water stress. This optional standard enables LPAs, through their Local Plans, to require additional water efficiency measures as a condition of granting planning permission. Some now use a tighter standard than 110 l/p/d, following a policy change in 2023 that allowed them to do so.

Currently, the measurement of the Water Efficiency Standard is done through a water calculator and fittings-based approach. The fittings-based approach sets maximum flow rates for fittings and fixtures like showerheads and taps.

The consultation notes that the actual water consumption in some new homes is far in excess of the minimum standards, up to 195 l/p/d. It suggests this could be because of the multifarious and unexpected ways that people use water in their homes, and/or that developments are not being built to the current minimum standards. Enforcement of Part G rests with Building Control bodies, which carry out approval checks during and after construction to ensure the required fixtures and fittings have been installed as intended. 

To reduce water demand from new homes, government proposes three changes in the consultation:

• Changing the minimum Water Efficiency Standard from 125 l/p/d to 105 l/p/d.
• Changing the optional technical standard from 110 l/p/d to 100 l/p/d, in areas where water stress is occurring or another local need is present.
• Revising the water calculator and fittings-based approach, to incorporate changes to water use and technology since the introduction of the initial building regulations. Specific revisions to each are detailed in the consultation document, pp.20-24. 

The consultation claims that these changes would create few additional burdens on housing developers, but does note the potential for unintended consequences. For example, it states that additional pressure on manufacturers could lead to delays in the delivery of new homes if the supply chain cannot align with the new minimum l/p/d standards in time. It also notes a risk of increased development costs, due to water efficient fittings being more expensive.

Subject to the outcome of the consultation and parliamentary approval, the government intends to implement the changes to Part G in 2026. It also proposes that the changes will be followed by a six-month transitional period. This means that the changes will likely take place alongside other amendments to planning policy and building regulations, such as updates to Part L and the Planning and Infrastructure Bill.

The consultation document also contains questions on the role of LPAs and Building Control bodies in delivering and ensuring compliance with Part G. It asks whether respondents think there are any issues with compliance in current housing developments, and if respondents believe that LPAs and Building Control bodies have effective procedures to deliver water efficiency measures. We would be interested in CIH member feedback on these questions, especially from members working in LPAs. 

The consultation document also includes a call for evidence on future reforms to Part G. The document discusses whether even more stringent l/p/d standards may be required in the future to meet housing need. This includes grey/black water reuse systems and rainwater harvesting systems, as well as wider changes such as public awareness campaigns and smarter leak detection measures.

CIH is interested in whether our members think more radical reform of Part G is required to meet housing need and protect the environment, and whether our members have any good practice examples of grey/black water or rainwater reuse systems they could share. We are also interested in any challenges members have experienced in incorporating reuse systems into housing developments, especially in relation to costs, skills shortages, and maintenance. 

We welcome feedback from CIH members on any part of the consultation on updating Part G. This will be used to inform our response to the consultation. CIH is specifically interested in member feedback on the following questions:

• Do you agree with the proposed reductions in the minimum and optional water efficiency standards?
• Do you agree with the proposed revisions to the water calculator and fittings-based approach set out in the consultation?
• Do think any of the proposed changes could create unintended challenges for the development of new homes, especially social and affordable homes?
  • This could be in relation to added costs, supply chain readiness, or anything else.
• Do you think LPAs and Building Control bodies have effective procedures to deliver water efficiency measures in line with Part G, or that there are any issues with Part G compliance in developments you have worked on?
• Do you have any views on whether black/grey and rainwater reuse systems should be incorporated into the building regulations for new homes?
  • We would also welcome any good practice examples or case studies of new developments with innovative reuse systems. 

Please email policyandpractice@cih.org by 3 December 2025 with any feedback.