There’s a running theme in water efficiency policy: everyone agrees the standard should be tighter, and nobody agrees on who should set it.
Earlier this month we covered Water UK backing Defra’s proposed cut from 125 to 105 l/p/d, and its argument for a single national standard rather than a patchwork of locally set numbers. The National Planning Policy Framework published on 17 August 2026 has now answered the second half of that question, and the answer is: not yet.
What the Framework says
Policy PM13 tells plan-makers that quantitative standards in local plans should not cover matters already addressed by Building Regulations. Water efficiency is one of only three carve-outs:
“Water efficiency, for which it may be appropriate to apply the tighter Building Regulations optional requirement where justified, or exceptionally a more stringent local standard in areas of serious water stress”
The plan-making climate policy reinforces it. Policy CC1 requires development plans to take a proactive approach to climate mitigation and adaptation, including by “setting local water efficiency standards for new development where these are justified in accordance with policy PM13”.
Two things follow from that wording.
First, the 110 route is explicitly endorsed. The Part G optional requirement of 110 l/p/d remains available to authorities that can justify it — which, in practice, is most of the south and east of England.
Second, and more interesting: “exceptionally, a more stringent local standard”. That is national policy sanctioning numbers below 110 in areas of serious water stress. It doesn’t say what those numbers should be, or how they’d be calculated, which leaves the door open for the 100 and 95 l/p/d policies that a handful of authorities have already pushed for.
The check on all of this is the same one applied to energy standards: the rationale must be justified and proportionate, and PM13 as a whole requires evidence that standards won’t undermine viability and deliverability.
Why this matters now
The timing is awkward in a useful way.
Defra consulted on cutting the mandatory Part G standard from 125 to 105 l/p/d, with a fittings-based compliance route, and the government response is still pending. If that lands, the national baseline moves below today’s optional requirement — and the whole optional-requirement architecture will need rethinking, because a 110 l/p/d “tighter” standard makes no sense once the mandatory floor is 105.
The NPPF doesn’t pre-empt that. It just keeps the local mechanism in place in the meantime. So for the next stretch, you’re likely to be working with:
- A mandatory standard of 125 l/p/d, heading for 105
- An optional standard of 110 l/p/d applied by many local plans
- A small number of authorities pressing for below 110 on serious water stress grounds
- No national consolidation of any of it
If you build across more than one authority, that’s three different numbers to track per site, plus the possibility of a fourth.
What it means for your calculations
The practical consequences are unchanged in kind, but sharper in degree.
The levers are the same as ever — shower flow rate, bath capacity, WC flush volumes, basin and kitchen tap flow rates, with rainwater and greywater reuse as the heavier tools. What changes is headroom. A specification that clears 110 comfortably may have very little left if a local policy lands at 100, and a bath plus a generous shower head will use most of that margin between them.
There’s also an evidence point worth noting for anyone responding to a local plan consultation. PM13 requires standards to be justified with proportionate evidence, and the “exceptionally” in the water clause is doing real work — it signals that sub-110 standards are meant to be rare and well-evidenced, not a default ambition. If a draft policy in your area proposes one without that evidence, the Framework now gives you clear language to point at.
What we’d suggest doing
Know your number per authority, not per company.
Run each standard house type through the official methodology at the standards that actually apply to your sites — 125, 110, and whatever the local plan is proposing — and find out which types have margin and which are living on the edge. One dwelling type covers every identical plot, so this is a small piece of work that maps your whole exposure.
WaterMonkey runs the full official Part G water efficiency methodology with 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 the site. We’ll add the new standard as soon as Defra confirms it.
If you’ve got a planning condition asking for something tighter than 110 l/p/d and you’re not sure it’s achievable with the specification you’ve priced, get in touch and we’ll tell you where the margin is.
Sources: National Planning Policy Framework, August 2026 (PDF), GOV.UK · Full steam ahead to fast-track more homes near stations — MHCLG press release, 17 August 2026 · Review of Water Efficiency Standards in the Building Regulations 2010 — Defra consultation