Backflow: Overview

B​ackflow protection for premises on a common supply

In some cases, premises such as blocks of flats, terraced housing, caravans, holiday homes, office blocks, industrial units and student accommodation are supplied via a common supply or distribution pipe.

To prevent backflow between these separately occupied properties in addition to point of use protection the local water undertaker may require the installation of what is sometimes referred to as secondary protection. This is in effect a form of wholesite protection to protect the supplies to neighbouring properties as well as the main.

Although the level of protection required will be determined by the local water undertaker, typically a double check valve is used for this purpose.




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Uncontrolled if downloaded. This is informative, non-statutory guidance and intended for general guidance purposes only; it is subject to change.

Compliance with this information should not be relied upon as guaranteeing no enforcement action will be taken by water undertakers. Water Regs UK accepts no liability for loss, indirect or consequential loss arising from or in connection with this guidance document.