12/14/2025
https://www.facebook.com/100085172202624/posts/822852947230438/
This image is a simplified cutaway diagram illustrating the rough-in installation of Drain-Waste-Vent (DWV) plumbing for a sink likely a kitchen or utility sink highlighting the use of a Double Fixture Fitting (or double-Tee/double-Wye) and the venting system.
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DETAILED DESCRIPTION OF THE PLUMBING SYSTEM
The diagram shows white PVC or ABS piping installed within and below the cabinet rough-in and the floor framing.
1. FIXTURE CONNECTIONS (THE SINK DRAIN)
* P-Trap (Visible): The drain stub-out coming from the back wall and connecting to the main drain stack shows the typical P-trap shape (the curved pipe that holds water to prevent sewer gases from entering the room).
* Cabinet Rough-in: The plumbing is positioned within a framed box that represents the space where the sink base cabinet will be installed.
2. MAIN DRAIN AND VENT STACKS
* Vertical Drain Stack (Right): A vertical pipe runs down from the P-trap passing through the floor and connects to the horizontal drain line below.
* Vertical Vent Stack (Center): A second vertical pipe is shown immediately behind the sink's drain. This is the vent pipe which is essential for equalizing air pressure in the drainage system. It runs upward (connecting to the main vent stack in the wall) and downward creating a re-vent or loop vent structure for the sink.
* Double Fixture Fitting (Double-Tee/Wye): The vertical pipe in the center has two inlets facing opposite directions suggesting it serves two fixtures on opposite sides of the wall (though only one sink drain is shown connected). It connects the drain line from the sink to the vent pipe and the main stack.
3. BELOW-FLOOR CONNECTIONS (HORIZONTAL DRAINAGE)
* Main Horizontal Drain: The largest pipe runs horizontally below the floor joists.
* Connection to Main Stack: The main drain stack from the sink drops below the floor and connects to the main horizontal drain line.
* Vent Connection: The vent pipe that drops below the floor (known as a loop vent or island vent in some specific kitchen layouts) connects back to the main horizontal drain but crucially it must connect above the centerline of the main drain pipe to act as a proper vent.
4. WALL FRAMING
* Wood Studs and Bottom Plate: The plumbing is roughed-in within standard wood-frame construction showing the vertical studs and horizontal bottom plates. A section of the wall to the left shows a vertical drain/vent stack connecting to a separate horizontal pipe indicating a parallel DWV system for another fixture in the bathroom or wall cavity (e.g. a toilet or shower).
The image emphasizes the complex but necessary arrangement of a properly vented sink drain to ensure smooth water flow and prevention of sewer gas entry.
