A toilet supply line usually leaks at one of its two ends: the nut that threads onto the shutoff valve at the wall, or the plastic nut that threads onto the fill valve under the tank. The most common causes are a nut that has worked loose, a nut that was overtightened and cracked, a worn washer inside the nut, or a line that is simply old. Sometimes the valve itself is weeping around the handle. Close the shutoff valve behind the toilet, dry everything, and replace the line. It's an inexpensive part.
Common Reasons a Toilet Supply Line Leaks
A loose nut. Bumping the line while cleaning can loosen either connection.
An overtightened nut. The nut at the fill valve is often plastic and only needs to be hand-tight. A wrench can crack it.
A cracked or worn plastic nut. Plastic gets brittle with age, and a hairline crack may only seep at first.
A worn washer or cone washer. Older lines seal with a rubber washer or cone that hardens over time. Once it does, tightening won't stop the drip.
A failing braided line. Frayed or rusty wires, kinks, bulges or a line stretched tight all mean replace it.
An old solid or plastic line. Rigid chrome or copper tubes and older plain plastic lines crack or corrode at the bends and fittings.
A weeping shutoff valve. If water shows up around the valve handle or stem rather than at the nut, the packing inside the valve is worn. That's a plumber's job.
Supply line maker Fluidmaster recommends inspecting the supply connector and replacing it if it's worn or more than 5 years old to prevent flooding and property damage.
Is It a Leak or Just Condensation?
In humid weather a cold supply line and tank can sweat, and drops roll down onto the nut and the floor. Wipe the line, valve and tank completely dry, lay a paper towel underneath and check back in 15 to 30 minutes:
Fine beads along the whole line or tank point to condensation.
Water coming back first at one nut, the valve stem or one spot on the line points to a real leak.
Water dripping from under the tank may be the tank bolts or the tank-to-bowl gasket, not the supply line.
If you can't find the source, the EPA's WaterSense program suggests reading your water meter before and after a two-hour period when no water is being used. If it changes, you probably have a leak. If the water only shows up around the base after flushing, that's a different problem, covered in our post on a toilet leaking from the base.
What to Do Right Now
Close the stop valve. It's the small valve on the wall or floor behind the toilet. Turn it clockwise until it stops, then flush once to empty the tank. If it won't close, or water keeps coming, use the main shutoff. Our post on how to turn off the water to your house shows where to find it.
Towel up and take photos of the puddle, the line and the valve.
Check below. If the bathroom is upstairs or over a finished basement, look for a stain, bubbled paint or a drip on the ceiling underneath.
Replace the line. Swap the whole line rather than chasing the drip. Fluidmaster's supply line instructions say to thread the metal nut onto the valve and snug it about a half turn past hand-tight, hand-tighten the plastic nut at the tank, then turn the water on slowly and check for leaks. If either end still drips, tighten it just enough to stop it. If the valve weeps or won't shut off, have a plumber replace it.
Supply line soaked the floor or the ceiling below? Call Blue Valley at (913) 395-8488. Open 7 AM–9 PM, every day.
When the Water Has Gone Past the Floor
A supply line leak is clean water, but it doesn't stay on top of the tile. It runs under the flooring, into the subfloor and along the joists, and wicks into baseboards and drywall. Signs it got further than the puddle:
A soft or spongy spot on the floor near the toilet
Swollen or separating baseboards, or peeling paint at the bottom of the wall
Loose tile, darkened grout, or vinyl that's lifting or stained
A stain or sagging drywall on the ceiling below
A small spill caught right away can often be handled with towels and a fan (see can I dry out water damage myself?). Once water is in the subfloor, the wall cavity or the ceiling, surface drying won't reach it. We use moisture meters to find how far it spread, remove only what can't be dried and set air movers and dehumidifiers until the readings are back to normal. See our structural drying and ceiling water damage pages, and our post on a ceiling water stain under a bathroom.
Edgerton Homes
About a third of Edgerton homes were built in the 1970s, where a toilet may still have an original valve or an older solid line. In newer homes, the supply line is often the one that went in with the house, well past the 5-year mark. Edgerton is served from our Olathe location. See our water damage restoration in Edgerton page for more.
Frequently Asked Questions
Can I just tighten the nut to stop the leak?
A gentle snug may stop a loose nut. If it still drips, stop. More force can crack a plastic nut or the fill valve. Replace the line.
How often should a toilet supply line be replaced?
Fluidmaster recommends replacing it if it's worn or more than 5 years old, and whenever you replace the fill valve.
Is a leaking supply line an emergency?
A drip you can stop at the valve can wait for a repair. A spraying line or a valve that won't close means shutting off the main right away.
Will insurance cover damage from a toilet supply line leak?
It depends on your policy and how the damage happened. A sudden break is often treated differently from a slow drip that went on for months. Ask your agent. We document the damage with photos and moisture readings.
Call Our Restoration Team
If a toilet supply line leak got into the floor, walls or ceiling of your Edgerton home, call Blue Valley at (913) 395-8488. Open 7 AM–9 PM, every day. We're IICRC Certified & Fully Insured. We'll check the floor and the ceiling below with a moisture meter, explain what can be dried in place and give you a free evaluation.