Frequently Asked Questions

Who is the calculator aimed at?

The calculator is aimed at any person or company undertaking a new build, major refurbishment or upgrade project that wishes to calculate water use based on litres used per person per day (lpppd).

Can I use the results from the calculator in a planning application?

Yes, planning authorities and Building Control will accept the calculation when it accompanies a planning application.

Why should I want to use the calculator?

The calculator has been designed to aid in the design and construction of a new bathroom, easy to use in a few simple steps, and can be saved or printed.

Can I save my results for later viewing?

Yes, the water calculator has the facility for you to register, save, use, or just print off the results. Saving allows you can go back into the project.

The product I want to use isn't in the list; can I enter my data/values manually?

Yes, the water calculator allows the user to insert product values over and above the database of products. Reading the ‘How to Use’ guide provides visual steps on how to do this under the custom tab.

Can the water calculator be used outside the UK?

The water calculator has been developed using the methodology set out by UK government building regulations which includes a ‘use factor’ formulae. The methodology allows the calculator to be used across other countries, plus provides the flexibility for the user to set own targets.

The Code for Sustainable Homes Technical Guidance and/or the Water Efficiency Calculator for new dwellings have been updated since I began my development, which version should I work with?

National and local governments have differing Building Regulations based on water scarcity – check which ones are applicable to your property. There is a ‘trend’ to look towards ‘fittings approach’ values not whole building approach, check which is relevant for your area/project.

How do I calculate how much my greywater harvesting system will contribute to my development?

To calculate this, you will need to enter 3 values into the calculator, the water usage of the fittings supplying your greywater system, the percentage of water to be recycled and the greywater demand.

To calculate the water usage of the fittings supplying your greywater system you will need to add together the water consumption of the fittings that will supply your grey-water system e.g. shower, bath and taps, excluding kitchen/utility rooms. To do this you can use the totals given in the water calculator in lpppd on the far right hand column.