The WRAS Type AB calculator tool app is an easy-to-use design aid for designers and installers. It provides details of overflow dimensions which theoretically should meet the performance requirements for rectangular type AB air gap arrangements with a single feed. Please note that compliance with the regulatory requirements can only be determined once an air gap arrangement has been installed.
To use this app you will need to know the size of the inlet valve and the width of the base of the overflow slot. The app suggests the minimum dimensions for the height of the overflow slot and the air gap distance to the inlet valve.
Users should note that full compliance can only be confirmed once additional checks suggested in the app have been made under normal operating conditions. Failure to satisfy these performance requirements will result in the need to make modifications to the installation for example, the air gap to the inlet valve may need to be raised to prevent fluids splashing on to it.
This tool uses the calculation methods and associated validation criteria set out in BS EN 13077:2008