Water Efficiency Calculations
We assess water consumption for new residential developments to ensure compliance with Part G of the UK Building Regulations, helping you meet sustainability goals and reduce costs.
Get a QuoteWhy Water Efficiency Calculations Matter
Water efficiency calculations estimate how much water a new development will use per person per day. They ensure compliance with Part G of the Building Regulations, help conserve resources, and reduce operational costs for occupants.
Key Factors Considered
- Flow Rates of Taps & Showers – Measures water usage from kitchen and bathroom taps.
- Toilet Flush Volume – Assesses water per flush (dual flush preferred).
- Bath & Shower Usage – Calculates typical water consumption per use.
- Dishwashers & Washing Machines – Standard consumption values if installed.
- Greywater & Rainwater Harvesting – Accounts for any water-saving technologies.
Water Efficiency Targets
Standard Requirement: ≤ 125 litres per person per day (L/p/d).
Optional Tighter Target: ≤ 110 L/p/d (some local authorities may require this).
How Calculations Are Done
Calculations follow Government-approved methodology based on installed fittings. If targets are not met, practical water-saving measures are recommended, including:
- ✅ Low-flow taps and showers
- ✅ Dual-flush toilets
- ✅ Water-efficient dishwashers/washing machines
- ✅ Greywater or rainwater harvesting systems
Optimize Water Efficiency for Your Project
Get a QuoteFrequently Asked Questions
1. What is a water efficiency calculation?
A water efficiency calculation estimates the daily water consumption of a new dwelling in litres per person per day (L/p/d). It considers fixtures and appliances such as taps, showers, toilets, baths, washing machines and dishwashers to demonstrate compliance with Building Regulations.
2. Are water efficiency calculations required for Building Regulations?
Yes. Water efficiency calculations are generally required for new residential properties in England to demonstrate compliance with Part G of the Building Regulations. The standard target is no more than 125 litres of water per person per day, although some developments may need to achieve a more stringent target of 110 L/p/d.
3. What information is needed to complete a water efficiency calculation?
Typically, details of the proposed sanitary fittings and appliances are required, including tap and shower flow rates, toilet flush volumes, bath capacities and the water consumption of washing machines and dishwashers. Details of rainwater harvesting or greywater systems should also be provided where applicable.
4. What happens if my development does not meet the required water efficiency target?
If the initial calculation exceeds the required target, suitable improvements can be identified to reduce water consumption. These may include lower-flow taps and showers, dual-flush toilets, more water-efficient appliances or rainwater and greywater systems.
5. When should I arrange a water efficiency calculation for my project?
It is best to complete the calculation during the design stage, when specifications for sanitary fittings and appliances can still be adjusted easily. A final calculation can then be prepared using the confirmed specifications to demonstrate Building Regulations compliance.