Toilet Supply Line Leaking
Updated February 25, 2026
Water dripping from the braided hose or chrome tube between the wall shut-off valve and the toilet fill valve -- caused by loose connections, worn washers, or a cracked line. This is typically a diy fix. Estimated cost: $5 - $10 for a new supply line.
Overview
A leaking supply line is one of the most common causes of water damage around toilets. The line is under constant pressure -- 40-80 PSI -- 24 hours a day. A small drip becomes a big problem fast. The good news: replacing the entire supply line takes 10 minutes and costs $5-$10 for a braided stainless steel hose. Do not try to patch or tape a leaking supply line. Replace it. The cost is trivial and the risk of failure is not worth saving $5.
Symptoms
- Water pooling on the floor behind or beside the toilet
- Drip coming from the connection at the shut-off valve or at the fill valve under the tank
- Water stain on the wall or floor near the supply valve
- Hissing sound from the supply line connection area
- Corrosion or mineral buildup visible on the supply line fittings
Common Causes
- Loose connection at the fill valve (under the tank) or the shut-off valve (at the wall) -- connections loosen over time from vibration and thermal cycling
- Worn rubber washer inside the coupling nut -- the washer compresses over years and no longer seals
- Cracked or corroded supply line -- chrome supply lines corrode internally; old plastic lines become brittle
- Cross-threaded connection from a previous installation -- never sealed properly
- Shut-off valve itself leaking from the stem packing or body -- looks like a supply line leak but the valve is the source
What You'll Need
How to Fix It
- Identify the Exact Leak Point
Dry everything with a towel. Lay a dry paper towel under each connection point: one at the shut-off valve, one at the fill valve under the tank. Wait 5 minutes. Check which paper towel is wet. That identifies whether the leak is at the top connection, bottom connection, or along the line itself. If the line itself is wet (not at a connection), the hose is cracked and needs replacement.
Tip: Toilet tank condensation can drip onto the supply line and mimic a leak. If the entire tank exterior is wet (condensation), dry the supply line and check it independently. Condensation is uniform; a leak is a single drip point. - Tighten the Connection (If at a Fitting)
If the leak is at a connection, try tightening first. Use an adjustable wrench or channel-lock pliers. Tighten the coupling nut at the leaking end by 1/4 turn. Do not overtighten -- the fill valve is plastic and the shut-off valve is brass; excessive force cracks the plastic or strips the brass threads. Check after tightening. Leak stopped? Done. Still dripping? The washer inside is worn.
Tip: If tightening stops the leak temporarily but it returns in a few days, the rubber washer is compressed beyond its ability to seal. Replace the supply line -- do not just keep tightening. - Replace the Supply Line
Turn off the shut-off valve. Flush the toilet to relieve pressure. Place a towel under the connections. Unscrew the supply line from the fill valve (under the tank) and from the shut-off valve. Water will drip -- have the towel ready. Take the old line to the hardware store to match the length and fitting sizes. Buy a braided stainless steel supply line ($5-$10). Connect the new line: hand-tight at both ends, then 1/4 turn with pliers. Turn the valve on slowly. Check both connections. No drips? Done.
Tip: Braided stainless steel supply lines are the standard replacement. They resist kinking, corrosion, and splitting. Do not buy chrome or plastic supply lines -- they fail more often and sooner. The $5-$10 braided line lasts 8-10 years.
When to Call a Pro
Call a plumber if the shut-off valve itself is leaking (valve replacement needed -- $100-$200), if the shut-off valve will not close (you cannot turn off the water to replace the line -- main valve shut-off first, then valve replacement), or if the fill valve threads are stripped and the new supply line will not seal (fill valve replacement needed).
Prevention Tips
- Replace toilet supply lines every 8-10 years as preventive maintenance. A $5-$10 hose is cheap insurance against a burst line that floods the bathroom.
- Use braided stainless steel supply lines, not chrome or plastic. Braided lines are rated to 5x the working pressure and resist corrosion.
- Check supply line connections annually. A quick visual inspection and a finger test for moisture takes 30 seconds per toilet.
- If you leave for vacation, turn off the toilet supply valves. A burst supply line in an empty house causes catastrophic water damage.
Frequently Asked Questions
What are the signs of a toilet supply line leaking?
Water pooling on the floor behind or beside the toilet Drip coming from the connection at the shut-off valve or at the fill valve under the tank Water stain on the wall or floor near the supply valve Hissing sound from the supply line connection area Corrosion or mineral buildup visible on the supply line fittings
What causes a toilet supply line leaking?
Loose connection at the fill valve (under the tank) or the shut-off valve (at the wall) -- connections loosen over time from vibration and thermal cycling Worn rubber washer inside the coupling nut -- the washer compresses over years and no longer seals Cracked or corroded supply line -- chrome supply lines corrode internally; old plastic lines become brittle Cross-threaded connection from a previous installation -- never sealed properly Shut-off valve itself leaking from the stem packing or body -- looks like a supply line leak but the valve is the source
When should I call a plumber for a toilet supply line leaking?
Call a plumber if the shut-off valve itself is leaking (valve replacement needed -- $100-$200), if the shut-off valve will not close (you cannot turn off the water to replace the line -- main valve shut-off first, then valve replacement), or if the fill valve threads are stripped and the new supply line will not seal (fill valve replacement needed).
How do I prevent a toilet supply line leaking?
Replace toilet supply lines every 8-10 years as preventive maintenance. A $5-$10 hose is cheap insurance against a burst line that floods the bathroom. Use braided stainless steel supply lines, not chrome or plastic. Braided lines are rated to 5x the working pressure and resist corrosion. Check supply line connections annually. A quick visual inspection and a finger test for moisture takes 30 seconds per toilet. If you leave for vacation, turn off the toilet supply valves. A burst supply line in an empty house causes catastrophic water damage.
When should I call a plumber for toilet supply line leaking?
Call a plumber if the shut-off valve itself is leaking (valve replacement needed -- $100-$200), if the shut-off valve will not close (you cannot turn off the water to replace the line -- main valve shut-off first, then valve replacement), or if the fill valve threads are stripped and the new supply line will not seal (fill valve replacement needed).
Can I fix toilet supply line leaking myself?
This problem is rated "DIY". Most homeowners can handle this with basic tools and patience.
How serious is toilet supply line leaking?
This is a high-severity issue. Address it immediately to prevent water damage or safety hazards.
How much does it cost to fix toilet supply line leaking?
The estimated repair cost is $5 - $10 for a new supply line. Costs vary by location, severity, and whether you hire a professional.
How can I prevent toilet supply line leaking?
Key prevention tips: Replace toilet supply lines every 8-10 years as preventive maintenance. A $5-$10 hose is cheap insurance against a burst line that floods the bathroom.. Use braided stainless steel supply lines, not chrome or plastic. Braided lines are rated to 5x the working pressure and resist corrosion.. Check supply line connections annually. A quick visual inspection and a finger test for moisture takes 30 seconds per toilet..