Guide for sizing Type AB air gap spillover

To use this guide you will need to know the size of the inlet and width of the spillover

This guide is only only for sizing rectangular overflows in cisterns supplied by a single inlet valve.

It should not be used for cisterns which provide a backup supply for alternative water systems e.g. grey or rainwater systems. How to create an acceptable air gap for this type of arrangement can be found here.

Further information about Type AB air gaps can be found here.

Important information

By using our guide, you agree that the information generated is for information purposes only and does not constitute definitive compliance advice. 

You understand that whilst every effort has been made by Water Regs UK to ensure accurate functioning of the calculator each installation is dependent on specific site and/or installation circumstances. Installing in accordance with the parameters calculated by our tool does not guarantee compliance with all applicable laws, regulations and byelaws.  

By using our guide, you agree that we make no claims, warranties, representations, promises or guarantees about the accuracy, completeness, or adequacy of the information generated. Water Regs UK shall not be liable for any losses resulting from non-compliance of any installation with the applicable laws, regulations or byelaws and any such responsibility and liability is expressly disclaimed.