Water efficiency policy: 110 litres per person per day

The 110 litres per person per day planning requirement is an optional building regulations standard that a council can only impose through an adopted local plan policy. Part G of the Building Regulations sets the ordinary standard for new dwellings at 125 litres per person per day, including 5 litres for external use. Where a planning condition applies the tighter optional requirement, that figure drops to 110 litres, and building control then checks it as part of the regulations rather than the council checking it as a planning matter.

So the question on any site is whether the local plan has adopted the standard, and whether the condition on your decision notice actually engages it.

The optional standard and how a council adopts it

Optional requirements were introduced by the housing standards review, and they work differently from ordinary building regulations. They only apply where a planning condition on the permission says they do.

National guidance on optional technical standards sets out what an authority has to show before it can impose the tighter figure. There has to be a clear local need, the requirement has to be viable, and the authority should allow a reasonable transition period. Water efficiency policies are usually justified on water stress, and the evidence base sits in the plan's supporting documents.

Where the policy exists, the condition follows automatically on residential permissions and there is little to argue about. Where it does not, a condition imposing 110 litres is open to challenge, because there is no policy basis for it.

The standard applies to new dwellings. Conversions and changes of use are treated differently under the regulations, so check which requirement applies to the work you are actually doing.

Water stress and why the policy exists

The Environment Agency classifies water company areas by level of water stress, and the areas classified as seriously water stressed cover much of the south and east of England. That classification is the evidence most authorities rely on.

The reasoning is straightforward. Where a water resource zone is already tight, new homes add demand that has to come from somewhere, and reducing per-person consumption costs less and arrives faster than new supply infrastructure.

For a self-builder, the policy is rarely the obstacle it first appears. Reaching 110 litres per person per day is a specification exercise rather than a design constraint, and the fittings that achieve it are widely available at ordinary prices.

The fittings approach and the water calculator

Approved Document G offers two ways to demonstrate compliance, and only one of them works for the tighter standard.

The fittings approach uses a table of maximum flow rates and volumes for each appliance. Specify within the table across the board and the dwelling is taken to comply. It is set up for the 125 litre standard.

The water efficiency calculator is the method that produces a figure. It takes the flow rate or volume of every fitting, applies fixed use factors, and returns a consumption figure in litres per person per day. For the optional 110 litre requirement, this is normally the route, because the calculation has to be shown rather than assumed.

The specification that usually gets there is unremarkable:

• A dual flush WC at 4 litres and 2.6 litres or better.
• A shower at 8 litres per minute or less.
• Basin taps at 5 litres per minute or less, with flow restrictors where necessary.
• A kitchen tap at 6 litres per minute or less.
• A dishwasher and washing machine within the calculator's stated volumes.
• A bath of modest capacity, since bath volume is the single largest variable in the calculation.

The bath is where most schemes fail. A large freestanding bath can put a dwelling over the figure on its own, whatever else is specified, so run the calculator before the sanitaryware is ordered rather than after.

Rainwater harvesting and greywater recycling can be counted, but the calculator applies rules to how much credit they attract, and for a single house the cost rarely justifies the saving compared with better fittings.

Water neutrality areas and the extra step

A small number of areas carry a stronger requirement than efficiency alone. In a water neutrality area, new development has to demonstrate that it will not increase the total demand for water in the affected zone, which means offsetting the new demand by reducing consumption elsewhere.

The best known example is the Sussex North water supply zone, where advice from Natural England led authorities to require water neutrality for new development. Schemes there need an offsetting strategy, usually through retrofitting fittings in existing properties or through a council-run mitigation scheme, secured before permission can be granted.

That is a different exercise from the 110 litre standard and it sits on top of it. If your site is in an affected zone, deal with it at the outset, because it affects viability and it cannot be conditioned away.

Nutrient neutrality is a separate matter again, concerned with wastewater rather than supply, and applying in different catchments. The two are often confused in conversation, and they need different evidence.

The condition and the evidence to discharge it

A typical condition requires the dwelling to be constructed to achieve no more than 110 litres per person per day, with evidence submitted before occupation.

Discharging it takes three things. The completed water efficiency calculator output for the dwelling, or for each house type on a small scheme. A schedule of the fittings actually installed, with model numbers and flow rates. And confirmation from building control that the optional requirement has been met.

Two practical points save time. Keep the specification consistent between the calculator, the building control submission and what the plumber installs, because a substituted shower head is enough to break the calculation. And where the condition is worded as pre-occupation, plan the evidence to be ready before completion rather than after the client has moved in.

Neighbourhood plans sometimes carry their own water efficiency or sustainability policies, and they form part of the development plan, as our note on when neighbourhood plans outrank the local plan explains.

How this sits alongside the energy work

Water efficiency and energy are assessed separately but they interact, and it is worth doing them together.

Hot water is a large share of the energy demand in a new home built to current fabric standards, so lower flow rates reduce both the water figure and the heating load. That relationship is worth stating in an Energy Statement where the local plan sets a carbon reduction target, because the same specification serves both policies.

Where the site relies on a private supply or where the water undertaker's capacity is in question, a Water Supply Assessment covers the connection and resource position, which is a different question from per-person consumption.

Order the work in this sequence. Confirm whether the policy is adopted, check whether the site is in a water neutrality zone, run the calculator against a draft specification, then fix the sanitaryware. Doing it in that order costs nothing. Doing it after the bathroom is ordered can cost a good deal.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.