The answer to 'what causes supply line' is that supply lines can become clogged or damaged over time, leading to leaks and water pressure issues. Supply lines are the flexible hoses that connect your plumbing fixtures, like sinks and toilets, to the main water supply. They can become blocked with mineral buildup or debris, or they can develop cracks and holes that cause leaks.
Some common causes of supply line issues include age, high water pressure, and mineral-heavy water. Over time, the rubber or plastic in the supply line can degrade, leading to cracks and leaks. High water pressure can also put stress on the lines and cause them to fail. And minerals in the water, like calcium and lime, can build up inside the lines and restrict water flow.