Changes to Part G water efficiency targets are on the way

DEFRA has published a consultation into changing water efficiency targets in Approved Document Part G in England.

There's also a Call For Evidence discussing further changes in the near future. The consultation is open until December 16th 2025. Details here:

Part G sets design limits for all new build homes in England and Wales, with lower targets enforced at local level.

https://consult.defra.gov.uk/water-efficiency-demand/review-of-water-efficiency-standards/supporting_documents/consultation-call-for-evidence-review-of-building-regulations-part-g2pdf

Current requirements:

🏠 New dwellings should be designed to use no more than 125 litres of water per person per day. This is lowered to 110 litres in areas more prone to drought.

🚽 Housebuilders either commit to install fittings with low flow rates, or use a calculator to predict the building's water use. The calculator was used for Code For Sustainable Homes (CSH) assessments in 2006, and hasn't been revised since.

Proposed changes:

🛀 Reduce targets to 105 litres, or 100 in drought areas. Both routes to compliance (Fittings Approach or Water Calculator) will remain, but the calculator with be refreshed with new occupancy assumptions, consider onsite leakage, and will remove external water use.

The Call for Evidence suggests lowering targets again in 5 years, or replacing targets entirely with a Mandatory Water Efficiency Label for the whole house.

MWEL is being introduced for all toilets, taps, showers and white goods next year.

Also up for discussion in the Call for Evidence:

🌧️ Mandatory rainwater harvesting in new homes

👷‍♂️ Creating a dual pipe network on new sites; one for waste, one for reusable water.

💩 (this is a new term for me...) Blackwater harvesting. In other words, using poo water to help your roses grow 🌹 🌺 

📉 Latest data shows we each use, on average, 137 litres in our homes every day. DEFRA want to reduce this to 110 litres by 2050.

🤔 Meanwhile, 19% of all treated water is lost to pipework leaks before it gets to our homes. That's around 3 billion litres a day across England and Wales.

So I'll end with a Sean Lock quote that feels apt:

"I feel like I've turned up at an earthquake with a dustpan and brush."

Part G changes will be published in 2026 with a 6 month transition.