Symptoms
- Water dripping or pooling near the wall behind the toilet
- Wet spot on the flexible line itself or at either end
- Corrosion or mineral buildup around the connection
- Leak worse when the toilet is actively filling
Likely causes
- CommonLoose connection at the tank or shutoff valveThe nut connecting the supply line hasn't been tightened enough or has loosened over time.
- CommonWorn or cracked supply lineOlder rubber or plastic lines degrade and crack, especially braided lines with a worn outer layer.
- PossibleCorroded shutoff valve or tank fittingMineral buildup or corrosion at the fitting prevents a tight seal.
What to do
- Turn off the shutoff valve behind the toilet before doing anything else.
- Dry the area completely, then turn the water back on briefly to see exactly where the leak starts.
- Try tightening the connection nut at the leaking end with an adjustable wrench, turning clockwise, snug but not overtight.
- If tightening doesn't stop it, turn off the water, disconnect the line, and inspect the washer or gasket inside the fitting for damage.
- Replace the entire supply line if it's cracked, corroded, or old, choosing a braided stainless steel line for durability.
- Reconnect, turn the water back on slowly, and check for leaks at both ends.
Tools and parts
- Adjustable wrench
- Towels
Braided toilet supply lineSearch: “braided stainless steel toilet supply line”
When to call a pro
A plumber isn't usually needed for a simple supply line swap, but call one if the shutoff valve itself is leaking or won't close fully.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.