The answer to 'why is my water line foul smell' is that a foul odor in your water line is usually caused by bacteria growth, mineral buildup, or a sewage backup. This can lead to unpleasant smells, discolored water, and potential health risks. Common symptoms include a rotten egg or sulfur-like smell, slimy water, and staining on fixtures.
The solution depends on the underlying cause. For bacterial growth, you may need to shock-chlorinate the water line. Mineral buildup can be addressed with a water softener or descaling treatment. If the issue is a sewage backup, you'll likely need professional plumbing services to locate and repair the problem. It's best to address a foul water smell promptly to prevent further issues.