12/30/2025
a detailed technical 3D cross-section diagram of a residential plumbing DWV (Drain-Waste-Vent) system. It illustrates how waste is moved out of a building while using a venting network to equalize air pressure and prevent sewer gases from entering the home.
The diagram uses "Drainage Fixture Units" (DFU) to calculate pipe sizing, which is a standard plumbing metric for load.
1. TOP FLOOR: THE BATHROOM GROUP
The upper section shows a standard bathroom layout where several fixtures share a common stack.
🔹 WC (Water Closet/Toilet): Labeled at 6 units. It uses a 3" drain that connects directly to the main soil stack.
🔹 Bath (Bathtub): Labeled at 2 units. It features a P-trap below the floor level to hold water and block sewer gases.
🔹 Basin (Sink): Labeled at 1 unit. It uses " piping for both the drain and the vent.
🔹 Total Bathroom Load: Noted as 6 units (this usually refers to the collective load of a standard "bathroom group" in many plumbing codes).
2. MIDDLE FLOOR: UTILITY AND KITCHEN
The middle section demonstrates how separate fixtures on a lower level tie into the vertical stack.
🔹 Wash Tub: Labeled at 2 units. It has a long horizontal run of " pipe.
🔹 Sink: Labeled at 2 units. It is served by a 2" drain line.
🔹 The Vent Stack: Labeled as having a total length of 25 ft and a recommended size of 2". This pipe runs parallel to the waste stack to provide air to the lower fixtures.
3. GROUND LEVEL AND MAIN INFRASTRUCTURE
This section shows the transition from vertical "stacks" to the horizontal "house drain."
🔹 The Main Stack: Labeled as carrying 10 total units over a length of 36 ft. The recommended size is 3".
🔹 Fresh Air Inlet: A dedicated 2" pipe that must be at least 1/2 the diameter of the main house drain. This allows fresh air to enter the system to keep the water seals in the traps from being sucked out by siphoning.
🔹 House Drain: The main horizontal line at the bottom. The text specifies it must be 4" in diameter because it receives the discharge from a water closet (WC).
🔹 House Trap: On the far left of the bottom pipe, there is a large U-bend (running trap) designed to prevent sewer gas from the municipal line from entering the building's internal piping.