How do I find a water leak

Water appears where gravity takes it, not where it escapes. A stain on a ceiling is usually some distance from the failure. Isolating sections of supply and watching the meter is the reliable method; guessing from the stain is not.

What actually happens

• Turn everything off and watch the meter: movement means a supply-side leak.
• Staining spreads along joists, so the visible mark is rarely above the fault.
• A leak that only appears in use is a waste-side fault, not supply.