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Water Efficiency
Calculations

Water efficiency calculations - Part G

What are water efficiency calculations?

All new homes in England must meet strict water usage requirements under Part G of the Building Regulations. These rules limit water consumption to no more than 125 litres per person, per day, with some local planning authorities requiring a stricter target of 110 litres, particularly in water-stressed areas.

Water efficiency calculations estimate the daily use per occupant, based on the number and type of fittings and appliances installed. Toilets, showers, baths, taps, dishwashers and washing machines are all assessed using the standard methodology in Appendix A of Approved Document G. The maximum consumption of each fitting is taken into account.

To gain Building Control approval, every new dwelling must submit a water efficiency calculation report. Without it, a completion certificate cannot be issued and occupation cannot legally begin. Getting this right early avoids project delays or the need to redesign.

If full product specifications are not yet chosen, we can provide a compliant schedule of fixtures to meet the legislative requirements. For developers, contractors and architects, this makes the process straightforward and reduces risk. At enevo, we supply fast, accurate assessments and practical recommendations so your project stays compliant, efficient, and on track.

Send us your project details and we’ll send a quote

Our water efficiency calculation services

Our service covers all requirements for Part G compliance, including:

We check architectural drawings and sanitary specifications to ensure all relevant details are included for calculation. Icon

Plan and specification review

We check architectural drawings and sanitary specifications to ensure all relevant details are included for calculation.
We establish whether your project must meet the 125-litre standard or the stricter 110-litre requirement. Icon

Local authority target confirmation

We establish whether your project must meet the 125-litre standard or the stricter 110-litre requirement.
We apply the Approved Document G methodology to predict daily water use per occupant. Icon

Detailed consumption calculation

We apply the Approved Document G methodology to predict daily water use per occupant.
Where adjustments are needed, we advise on product choices or design changes to achieve compliance. Icon

Compliance recommendations

Where adjustments are needed, we advise on product choices or design changes to achieve compliance.
If fixtures and fittings are not yet specified, we provide compliant product schedules to keep your project on track. Icon

Product schedule support

If fixtures and fittings are not yet specified, we provide compliant product schedules to keep your project on track.
We prepare formal calculation reports suitable for submission and approval, ensuring completion certificates can be issued. Icon

Building Control reporting

We prepare formal calculation reports suitable for submission and approval, ensuring completion certificates can be issued.
For urgent projects, we offer a 24-hour turnaround option to help you meet tight deadlines. Icon

Fast-track service

For urgent projects, we offer a 24-hour turnaround option to help you meet tight deadlines.
We check architectural drawings and sanitary specifications to ensure all relevant details are included for calculation. Icon

Plan and specification review

We check architectural drawings and sanitary specifications to ensure all relevant details are included for calculation.
We establish whether your project must meet the 125-litre standard or the stricter 110-litre requirement. Icon

Local authority target confirmation

We establish whether your project must meet the 125-litre standard or the stricter 110-litre requirement.
We apply the Approved Document G methodology to predict daily water use per occupant. Icon

Detailed consumption calculation

We apply the Approved Document G methodology to predict daily water use per occupant.
Where adjustments are needed, we advise on product choices or design changes to achieve compliance. Icon

Compliance recommendations

Where adjustments are needed, we advise on product choices or design changes to achieve compliance.
If fixtures and fittings are not yet specified, we provide compliant product schedules to keep your project on track. Icon

Product schedule support

If fixtures and fittings are not yet specified, we provide compliant product schedules to keep your project on track.
We prepare formal calculation reports suitable for submission and approval, ensuring completion certificates can be issued. Icon

Building Control reporting

We prepare formal calculation reports suitable for submission and approval, ensuring completion certificates can be issued.
For urgent projects, we offer a 24-hour turnaround option to help you meet tight deadlines. Icon

Fast-track service

For urgent projects, we offer a 24-hour turnaround option to help you meet tight deadlines.

Our water efficiency calculations process

01

Initial consultation
Send us your project drawings and specifications, and we will review and confirm what information is needed.

02

Requirement review
We establish whether your project must meet the 125-litre standard or the stricter 110-litre requirement.

03

Calculation of usage
Daily water use is calculated across all specified fittings and appliances, using the Approved Document G method.

04

Compliance advice
If changes are needed, we provide clear recommendations or compliant product schedules to secure a pass.

05

Final report and support
We issue your calculation report for Building Control and assist with any queries through to sign-off.
Why enevo for water efficiency calculations? Image
Why enevo for water efficiency calculations? Icon

Why enevo for water efficiency calculations?

  • Proven track record: over 1,000 dwellings assessed with a 100% pass rate.
  • Expert knowledge: calculations follow Approved Document G methodology in full.
  • Practical support: compliant product schedules provided if items are not yet specified.
  • Client-first approach: no charge for failed calculations, plus clear guidance to achieve compliance.
  • Fast turnaround: quick and affordable service, with 24-hour options available.
  • Trusted expertise: experienced in supporting projects of all sizes across the UK.

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Testimonial IconTrusted, Time And Time Again

5 Star Rating

Harry gave me excellent advice and clear understanding on what BREEAM means as well about the specific accredited assessing required by professionals like Harry.

Angela Singh

5 Star Rating

Very efficient and professional service. Cant recommend enevo enough, glad I chose them for my project.

William Brannon

5 Star Rating

Very impressive on all aspects of energy calcs. Responsive and cost competitive. Highly recommended

Nick Spencer

5 Star Rating

enevo are always helpful, friendly and efficient in carrying out SAP calculations for our clients.

Lizzie Hicks

5 Star Rating

Dan at enevo has completed for us SBEM Calculations and EPC Certificates for 6 commercial units on an industrial estate. The cost of the works was very competitive and the service we received was second to none. With very limited time to get these works completed Dan worked round the clock (and into his annual leave!!) to ensure that our completion date was achieved with very little notice. Would highly recommend!

Mollie Belton

5 Star Rating

We have always found enevo to provide an excellent service in the preparation of SAP Calculations and Assessments as well as EPC Certificates for projects that they have worked on for us. They are also reasonably priced so we would certainly recommend them to anyone looking for this type of service.

Martin Booker

5 Star Rating

Used enevo from start to completion of our recent project of 2No. new builds. Services included SAP/EPC and property air testing. Great service, understanding of requirements and cost. Person friendly company and good with communication.

Mark Radcliffe

5 Star Rating

Very efficient, personal, professional service, with a quick report turnaround. Highly recommended if you're a self-builder trying to navigate the complexities of the latest regulations.

Edward Broadhead

5 Star Rating

Always efficient and prompt service, enevo are an asset to my company, having used their services on multiple developments I wouldn't hesitate to recommend them.

Mac Chappell

5 Star Rating

Great service with a fast turnaround. Communication was excellent throughout. Richard the engineer was polite and professional. Will certainly be using enevo again.

ECO PROPERTY DEVELOPMENTS LTD

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Water Efficiency Calculations

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Water Efficiency Calculations

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