You already read a lot of labels: SAP bands, energy ratings, the U-value on a window schedule. There’s a new one on the way, and this time it’s on the fittings themselves — the taps, showers and WCs that decide whether your Part G calculation passes.
The government is introducing a mandatory water efficiency label: an A–F, colour-coded rating — much like the energy label on a fridge — that has to be shown on water-using products at the point of sale.
What’s actually being introduced
The scheme is the Mandatory Water Efficiency Labelling Scheme (MWELS), brought in under powers in the Environment Act 2021. In short, it puts a standard, comparable water-efficiency rating on the products people buy.
The headline points:
- A single A–F colour-coded label showing how much water a product uses, so two showers or two WCs can be compared like for like.
- It covers the usual suspects — taps, showers, toilets and urinals, dishwashers and washing machines.
- The obligation sits with the trade: suppliers test their products, work out the banding and produce the label; dealers (retailers and merchants) have to display it clearly at the point of sale.
- It’s built on the international standard ISO 31600:2022, and it applies UK-wide — England, Scotland, Wales and Northern Ireland.
The reasoning is the same one driving the Part G reform: England is short of water, and demand from new homes has become a genuine constraint on where and how much you can build. A label won’t save a drop on its own, but it makes the efficient choice the obvious one on the shelf.
Where it stands right now
This is coming, not here. The regulations were laid before Parliament on 6 May 2026 as a draft affirmative instrument — meaning both Houses have to approve them before they take effect — with the intention of the scheme coming into force by the end of 2026.
So nothing changes on your current jobs today. But the direction is set, and the timing is worth noting: the label is arriving in the same window as the proposed cut to the Part G standard from 125 to 105 litres per person per day. Two separate pieces of policy, pointing the same way, landing at roughly the same time.
It’s not landing without argument
Worth being straight about: the industry isn’t uniformly behind the detail. The Builders Merchants Federation has flagged the risk of consumer confusion, given there’s already an established voluntary label (the Unified Water Label) in the market — and a second, mandatory scheme sitting alongside it could muddy rather than clarify. Appliance manufacturers have raised concerns about cost and about whether a single metric fairly represents how products like dishwashers actually perform.
There’s a deeper point too, and it’s one assessors will recognise. A recent University of Surrey study (with input from Mira Showers) made the case that flow rate on a label doesn’t equal real-world consumption: push flow rates too low and people take longer showers, or tamper with the fitting, and the saving the label promised quietly disappears. The label tells you what a product can do, not what a household will actually do with it — which is exactly the gap the Part G calculator’s fixed-use assumptions try, imperfectly, to bridge.
What it means for you
For assessors and specifiers, the useful bit is the join between this and Part G. The water calculator has always run off the specified fittings — shower flow rate, bath capacity, WC flush volume, tap flow rates. A consistent, mandatory label makes those inputs easier to source and easier to evidence: instead of digging through manufacturer datasheets for a flow rate, you’ll increasingly have a standard rating to point to.
It also sharpens the compliance question that Defra has already raised — whether the fittings on the drawings are the fittings that actually get installed. When every product on site carries a visible rating, the gap between the specified spec and the fitted spec gets harder to hide.
None of this changes your method today. 125 l/p/d remains the standard you calculate to, with 110 l/p/d where a Local Plan requires it, until the Part G reform is confirmed. But if you’re specifying fittings for schemes that will complete in 2027 and beyond, it’s worth getting into the habit now of choosing products on their water rating — because the margin between a comfortable pass and a fail lives entirely in those numbers.
What we’d suggest doing
Know your number before the standards tighten. Run your standard house types through a proper Part G calculation and see which ones still pass with headroom — a fittings spec is far cheaper to adjust on paper than after a Building Control inspection.
WaterMonkey does exactly that: the full official water efficiency methodology, live PASS/FAIL as you type at 125 or 110 l/p/d, rainwater and greywater included, free in your browser. Building Control-ready PDF reports are £25 +VAT, and one dwelling type covers every identical plot on a site — so a whole estate needn’t cost the earth. We’ll factor the new labelling in as the scheme and the revised Part G methodology are confirmed.
If water is already the sticking point on one of your sites, get in touch and we’ll tell you how we’d approach it.
Sources: UK mandatory water efficiency labelling — Defra consultation and outcome (gov.uk) · United Kingdom: New Mandatory Water Efficiency Labelling (MWEL) Regulations — Product Compliance Institute, 6 February 2026 · The Mandatory Water Efficiency Labelling (MWEL) Regulations 2026 — TÜV Rheinland · Water efficiency labelling alone won’t deliver Britain’s water-saving ambitions — Builders Merchants Journal, 27 July 2026