A plumber is installing a bidet attachment on an existing toilet in a residential bathroom. The bidet is designed to connect directly to the toilet's cold water supply line. To comply with plumbing codes and prevent contamination of the potable water supply, which of the following is the most appropriate backflow prevention method for this bidet installation?
- AA pressure vacuum breaker (PVB).
- BA double check valve assembly (DCVA).
- CAn air gap.
- DAn atmospheric vacuum breaker (AVB).
Show answer & explanationAnswer & explanation
Correct answer: C. An air gap.
For a bidet attachment that could potentially be submerged in contaminated water (e.g., in the toilet bowl), the highest level of backflow protection is required. An air gap provides the most reliable protection by physically separating the potable water supply from the potential source of contamination. While some bidets may incorporate integral AVBs or DCVAs, an actual physical air gap is the most robust and preferred method where feasible, or a bidet specifically certified with an integral air gap or compliant backflow preventer.
Why the other options are wrong
- A. A PVB is for high-hazard situations but requires a continuously pressurized supply and cannot be subject to backpressure, which could occur with a submerged bidet. It's also typically installed outdoors or where spillage is acceptable.
- B. A DCVA is suitable for low-hazard situations, but a bidet connected to a toilet bowl represents a high-hazard cross-connection, requiring greater protection.
- D. An AVB is suitable for high-hazard situations but cannot be under continuous pressure, cannot be subject to backpressure, and must be installed above the flood level rim, which might not be consistently achievable or reliable with all bidet designs.
Bidet Backflow Protection
The necessary measures to prevent contaminated water from a bidet or toilet bowl from siphoning or flowing back into the potable water supply.
- Bidet attachments are considered a high-hazard cross-connection.
- Requires the highest level of backflow protection.
- Air gap is the most reliable method, often integral to compliant bidet designs.
Memory trick: Bidet bowl, water's call, air gap stands above it all.