The answer to 'toilet foul smell' is that a foul odor coming from your toilet is usually caused by a buildup of bacteria, mold, or other organic matter in the toilet bowl or plumbing system. Common causes include a clogged drain, a damaged wax ring, or a problem with the sewer line.
Symptoms of a toilet foul smell can include a persistent unpleasant odor, gurgling noises, or slow draining. Solutions may involve plunging the toilet, using a toilet auger to clear a clog, or replacing the wax ring. If the problem persists or you suspect an issue with the sewer line, it's best to call a professional plumber to diagnose and fix the issue.