We stopped using the plumbing and called an emergency plumber. Using a small inspection camera, he discovered thick maple roots growing through a cracked section of our underground sewer pipe. The roots had formed a tangled blockage that trapped toilet paper and waste, while several sections of the old pipe had shifted enough to allow wastewater to leak into the surrounding soil.
The plumber explained that the damage had been developing for years and could eventually have caused sewage to back up throughout the house. Fixing it required excavation, removing the invading roots, and replacing the damaged part of the sewer line. The cost was far higher than we expected, but by that point it was clear that a simple home remedy could not repair a cracked or displaced pipe.
I felt embarrassed about relying on the salt trick, but the plumber said many homeowners try internet remedies before calling a professional. He also warned that salt is not a dependable solution for serious sewer problems and may create additional environmental or plumbing concerns. We ultimately repaired the damaged line, and the experience taught me an important lesson: persistent gurgling, sewage odors, slow drains, or bubbling toilets should be investigated early instead of covered up with a quick DIY fix.