Short definition
A bidet is a fixed bathroom fixture for personal hygiene cleansing of the perineal area, typically installed beside the toilet. Two designs exist: over-rim (a faucet fills the bowl from above, low backflow risk) and ascending-spray (water jets upward from a fixture-mounted sprayer toward the user, higher backflow risk). The standalone fixture is rare in modern US bathrooms — most US bidet installs are bidet seats or bidet toilets that retrofit onto an existing toilet.
What it is
A traditional bidet is a low porcelain bowl with hot and cold water connections, mounted on the floor next to a toilet. The user sits or stands over the bowl after using the toilet and uses the water for hygiene rinsing. Two mechanical types are in use:
Over-rim bidet — works like a low-rim sink. A faucet fills the bowl from above. Backflow risk is low because the supply outlet is well above the flood-level rim, exactly the same protection a lavatory uses.
Ascending-spray bidet — water jets upward from a sprayer at the bowl bottom, toward the user. The discharge point is potentially submerged when the bowl fills. That creates a cross-connection risk if the fixture isn’t equipped with backflow protection — water from the contaminated bowl could be siphoned back into the supply during a pressure drop.
In the US market, the standalone bidet has effectively been replaced by bidet seats and bidet toilets — products that integrate the spray-wash function into a regular toilet. The newer fixtures certify built-in backflow protection to ASME A112.18.1 / CSA B125.1, plus the toilet’s existing fill-valve protection.
Why it matters to a homeowner
Three things drive most US-homeowner bidet questions in 2026:
Standalone vs. retrofit. If you’ve moved to the US from Europe or Latin America, you’ll find the separate bidet fixture rare. The mainstream US choice is a bidet seat (replaces the seat on an existing toilet, taps the toilet supply, plugs into a GFCI outlet) or a bidet toilet (one integrated fixture). See the bidet-toilet entry for that path.
Hand-held bidet sprayer with no vacuum breaker. The cheapest retrofit — a flexible sprayer hose tee’d into the toilet supply line — is also the most commonly mis-installed. The trade rule is that a hand-held bidet sprayer must have an ASSE 1001 vacuum breaker at the supply tee, because the sprayer can be left submerged in the toilet bowl and create a cross-connection. Many DIY kits sold at big-box stores include the vacuum breaker; verify before relying on it.
Backflow protection in code. Under the IPC and UPC code basis Washington adopts, water supply to a bidet must be protected against backflow by an air gap or backflow preventer. For ascending-spray fixtures, the minimum protection is an atmospheric vacuum breaker (ASSE 1001) or pressure vacuum breaker (ASSE 1020). For over-rim bidets, the standard lavatory air-gap rule applies (faucet outlet at least 1 inch above the flood-level rim).
Common variants and what a bidet is not
- Standalone bidet vs. bidet seat or bidet toilet. Standalone is a separate floor-mounted bowl. Bidet seat replaces a regular toilet seat. Bidet toilet integrates the fixture and the spray.
- Hand-held bidet sprayer. The cheapest retrofit; flexible hose with pistol-grip sprayer mounted near the toilet. Backflow protection required at the supply tee.
- Over-rim vs. ascending-spray. Different backflow risk profiles, different code-compliant protection.
- Bidet vs. lavatory. Bidet is for hygiene, lavatory is for hand washing. Code treats them differently — backflow rules apply to bidets, not lavatories.
Common failure modes
- Backflow protection bypassed during retrofit. Owner installs a hand-held sprayer on the toilet supply with no vacuum breaker. Cross-connection hazard if the hose is left submerged. Fix: add an ASSE 1001 vacuum breaker at the supply tee.
- Trap dry-out. Standalone bidets in vacation homes; the trap evaporates and sewer gas enters the room. Same fix as any unused trap (water periodically).
- Spray-mechanism mineral scale. Hard water deposits clog the ascending-spray nozzle. Vinegar soak.
- Hand-held sprayer hose cracks in retrofit setups. Replace.