The answer to 'what causes water line' is that there are several common causes of issues with a home's water lines. The most frequent causes include freezing temperatures, corrosion, tree root intrusion, high water pressure, and old age or wear and tear on the plumbing system. Freezing can cause water lines to crack or burst, while corrosion over time can lead to leaks. Tree roots can grow into and damage underground water lines, and high water pressure can put excessive stress on the pipes. Additionally, older plumbing systems simply become more prone to problems as the materials degrade.
If you're experiencing water line issues, it's best to have a professional plumber inspect the system to identify the root cause and recommend the appropriate repairs or replacement. Trying to DIY water line fixes can be risky and lead to further damage if not done properly.