water flowing up hill

[CHARLIE VAN FLEET]

guys
wonderful p-trap drain on sink today

cvf

[ROBERT YOUNG]

Lol. Ingenuity is the mother of invention.

Plumbing Traps (https://montreal-home-inspection-services.com/blog/plumbing-traps), P-Trap
Just below a Sink or Wash Basin is the Tail Piece. An Inlet drainpipe mounted just above the Trap Adaptor connected to the Plumbing Trap.
The Plumbing Trap below the Trap Adapter in this image is referred to as a P-Trap, which in of itself, is a Plumbing Fixture and device.
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P-trap consists of the Inlet, Trap Adapter, Top & Lower Dip, P-Trap, Cleanout, Trap Weir Seal or Crown Weir Seal below the Trap Crown, Outlet and Trap Arm.
A Plumbing Trap, by definition, is a device that retains a measured amount of water. When, in this case, lavatory fixtures are utilized, an amount of water is retained in the P-Trap while the rest of the water is drained. The water that remains in the P-Trap device is referred to as, The Trap Seal.
P Trap serves several functions.
1: Backflow prevention.
2: Trap Debris.
The Trap Seal serves several functions.
1: Prevent Sewage Odors & Gases, a complex mixture of toxic and nontoxic gases produced and collected in sewage systems, from escaping/dispersing into the room.
2: Impeding Vermin, Mice and Insects from exiting the drainpipe into your home.