Backflow protection: FAQs
What backflow protection is required for a combined toilet and bidet?

All water fittings in a bathroom must be supplied via an appropriate and adequate form of backflow protection, one which is rated either equal to or higher than the highest downstream contamination risk (fluid category) for the type of backflow (back pressure or back siphonage) it is likely to be exposed to.
A combined toilet and bidet is considered to be a fluid category 5 risk.
The installation of a combined toilet and bidet is notifiable in Scotland and Northern Ireland and could be notifiable in England and Wales as either a bidet or a material change of use. If notification is not required, for example because it is undertaken by an approved contractor, there remains a legal obligation for the premises owner or occupier to ensure the plumbing work is fully compliant with the water fittings regulations, byelaws in Scotland.
Some combined toilet and bidets incorporate backflow protection. Where this is the case, it is essential to confirm it meets all UK requirements, which is why it is so important to take advantage of the notification check offered by water undertakers.
If there is no acceptable built in backflow protection the installation must be supplied via a suitable form of fluid category 5 backflow prevention, for example via a break tank arrangement incorporating a Type AB air gap.
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Disclaimer
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.