Backflow prevention for smart toilets & bidets
Backflow prevention is a vital part of the installation of smart toilets and bidets that your plumber needs to consider to mitigate any chance of contamination to the water supply.
Cross-connection is the contact between a drinking water supply system and any equipment which may make it possible for contaminated water to enter the drinking water system (AS/NZS 3500 Part 1 Water Services).
Cross-connection can occur when backflow causes the contaminated water to flow back into the main water supply. Backflow occurs when there is a sudden drop in the pressure of the water main outside your home or if the water pressure in your home is higher than at the main. This could cause the water in your toilet or bidet to be drawn back into the main water supply. This can cause potentially dangerous contaminants to pollute your drinking water.
A backflow prevention device can be installed to ensure no cross-connection takes place and contaminated water does not get into your main supply. It is therefore essential for your plumber to install a backflow prevention device when installing your smart toilet or bidet.
Backflow prevention devices have one of the following components to stop water flowing backwards:
- A valve that only lets water go in one direction
- An air gap
- A break tank
Hazard ratings for smart toilets and bidets
The hazard rating of the source of contamination will dictate the kind of backflow prevention device that is required. The hazard rating is decided in accordance with AS-NZS 3500-1 Section 4.3: Cross-Connection Hazard Rating.
Cross-connections are rated using three levels of hazard:
- High Hazard - where the contamination of the water supply has the potential to cause death.
- Medium Hazard - where contamination of the water supply has the potential to endanger health.
- Low Hazard - where contamination of the water supply would cause a nuisance, but would not endanger health.
The Office of the Technical Regulator (OTR) has labelled the cross-connection hazard rating as a high hazard for smart toilets or bidets. High hazard cross-connections must have a break tank, reduced pressure zone or air gap installed.
Do smart toilets and bidets need backflow prevention?
A smart toilet or bidet must comply with AS/NZS 3500 Part 1 Water Services Clause 12.2.3.
In accordance with this legislation, if a douche outlet is installed at least 25mm above the overflow level of your toilet bowl, it does not require a backflow prevention device. If the douche outlet is less than 25mm above the overflow level, a ‘high hazard’ backflow prevention device that adheres with AS/NZS 2845.1 or AS 2845.2 must be installed.
(NSW Fair Trading Plumbing Advisory on Installation of Toilet Seat Douche Outlets, May 2021).
