The answer to 'pipe foul smell' is that a foul odor coming from your pipes is usually caused by a buildup of bacteria, mold, or sewer gas. Common symptoms include a rotten egg or sewage-like smell, and the odor may be worse when running water or using fixtures. Some solutions include cleaning the drain, fixing leaks, and properly venting the plumbing system.
If the smell persists or you're unsure of the cause, it's best to call a professional plumber to diagnose and fix the issue. They can use specialized tools and techniques to identify the source of the odor and recommend the appropriate repairs. Attempting DIY fixes without proper knowledge could make the problem worse or create safety hazards.