deep-seal trap

deep-seal trap, antisiphon trap

In plumbing, a U-shaped trap having a seal, 3 of 4 in. (10 cm) or more.
References in periodicals archive ?
Connect them with a combined waste-and-overflow unit that incorporates a deep-seal trap.
Replace vulnerable traps, such as those connected to floor drains that are likely to fail through evaporation, with deep-seal traps (consisting of a 4-inch, rather than a 2-inch seal), or install trap seal primer valves that can detect and prime dry traps.
Retrofit all building U-traps with deep-seal traps or trap seal primer valves.