Part G Water Efficiency Calculations

Encouraging water conservation through smarter water usage targets

Water conservation is vital to a more sustainable future, the water efficiency of a property is becoming increasingly important in making homes more sustainable. 

What are Part G Water Efficiency Calculations

Water efficiency calculations are required for all new-build dwellings to comply with Part G of the building regulations, which covers sanitation and hot water safety.  To comply, a property must show that its water usage will not exceed 125 litres/person/day. 

Please note, some local planning bodies, especially in London and South East may stipulate lower water consumption targets, for example, the London Plan has a current target of no more than 110 litres/person/day. 

The flow rates of the following are taken directly into account

  • Bathroom Taps
  • Dishwashers
  • Washing machines
  • Kitchen Taps
  • Shower
  • WCs
  • Utility Taps

Also taken into account are

  • Water softeners
  • Bath volume
  • Waste Disposal Units
  • Rain/Grey Water Harvesting

What’s the Part G process, and when will I need it?

Normally, building control will request a water efficiency calculation to be carried out at design stage as well as the as-built stage.  The design stage is carried out to confirm that the development can meet the required target. Using a combination of default values and actual specification (where it is available), our dedicated team of specialists will carry out the calculations and demonstrate building regulations will be met. If it fails to meet the target at the first attempt, we will advise and provide solutions to ensure compliance is met.  

The as-built stage is a little more detailed. Rather than using default figures/flow rates, we need the actual flow rates of the sanitary ware and the specification of the washing machine and dishwasher.  This information is notoriously difficult to come across in manufacturers’ literature, fortunately for you, included within our costs is a full support service, you simply give us the make and model - and we’ll do the rest.

On completion, you will be provided with a full report that can be forwarded to building control to demonstrate compliance.

What information will I need to provide for a water efficiency calculation?

At design stage we will require the following;

  • Floor plans showing the number of ‘wet rooms’ such as the kitchen, utilities and bathrooms.
  • In addition, the plans will also need to show the number of water ‘points’, such as showers, toilets, sinks, washing machine or dishwashers.

At as-built stage we will require the following;

  • As-built set of drawings
  • Our As-built Water Confirmation sheet completed and returned, please click here to link to it

We have been leading providers of Part G Water Calculations since they became part of regulations back in 2015, if you would like to contact our dedicated in-house team to discuss your development and requirements, please get in touch here or via the quick quote link below.

Get in touch

Melin Energy Consultants

01554 571010

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