P-Trap Example

P-Traps are used to prevent back-flow from waste pipes back into fixtures and cross connections.

P-Traps work by using water pressure to prevent gasses from traveling back from waste pipes or sewers into the fixture.

The top of the water stored in the p-trap to prevent back-flow (the top of the water seal) is called the crown weir.


This P-Trap example is a 11/2" plastic p-trap from Home Depot:

Parts of the P-Trap in the bag.

Parts of the P-Trap included in the bag.

Inside and Outside Diameters of Connective Pieces.

End to End measurement, Outside and Inside Diameter of Wall Tube connecting P-Trap to waste pipe.

P-Trap and Waste Tube with Connective Pieces.