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Short Summary
Main recommendation: Have the sagged drain line replaced by opening the bathroom floor, trenching, replacing the pipe, and remodeling the bathroom, and remove the house trap while doing so. The bouncing toilet water and sewer smell were traced to air being forced through a water-filled, sagged section of pipe because the vent was blocked, not to a simple clog. The camera and locator work showed about 12 feet of standing water between 3 and 15 feet from the access point, separate from the earlier 22-foot location of the house trap.
Key Points
- The bouncing toilet water signals a venting problem: displaced air has no clear exit through the roof, so it pushes back through the system.
- A camera inspection found a water accumulation about 22 feet down the drain (the distance to a mysterious upward-turning pipe), which should not be present in a properly pitched drain line; later camera mapping showed standing water between 3 and 15 feet from the access point.
- A house trap (also called a rat trap) holds water as a seal, which blocks a drain snake from reaching past it, so a clog beyond it cannot be cleared that way.
- The pipe appears to have sagged, likely because the sand bedding under the old cast iron joints shifted, creating a second water trap in the line.
- Trapped air then bubbled up through toilet water seals, which the host links to the sewer odor.
Details Worth Noting
- Concrete instructions: The host's recommended fix is to open the bathroom floor, trench it, replace the sagged pipe, and remodel the bathroom, while removing the house trap so the new pipe pitches properly, vents properly, and can be cleared with a snake later. Diagnostic steps shown were: run a camera down the vent stack and then the drain; cut into the concrete at the access door and dig; use a camera locator with a transmitter to mark the camera head's position (it was found 2 feet 8 inches deep); flush the upstairs toilet and watch the trap's water level to test for restriction; then pull the camera back in 3-foot steps to map where the water sits.
- The locator method places one red marker under the camera head and another at the opposite magnetic pole, then marks the midpoint (yellow) as the camera's exact location.
- Standing water in the trap was seen between roughly 3 and 15 feet, meaning about 12 feet of the pipe was affected.
- The host notes that the house trap is an older design, sometimes used to block rodents coming up from cesspools, and has fallen out of favor because it prevents easy clearing of blockages.
- The demonstration model shows that a properly vented fixture requires a separate vent path so air can escape; here the wet vent path was blocked by the sagged, water-filled section.
Bottom Line
The bouncing toilet and sewer smell come from a sagged, water-filled drain section that traps air, so the lasting fix is structural replacement rather than a simple clean-out.
