How to Fix a Leaky Toilet: Find and Stop the Leak

What You’ll Need

Towels or a sponge and a small bucket
Flashlight and dry paper towels
Adjustable wrench or pliers, used gently
Screwdriver, if the toilet’s parts require one
Replacement part suited to the toilet: commonly a flapper, fill valve, supply line, or wax ring
Disposable gloves; safety glasses are useful when loosening fittings

Take a clear photo of the tank’s parts and note the toilet brand or model before shopping. Toilet components are not universally interchangeable. Avoid using a wrench on plastic nuts unless the part instructions call for it.

Step-by-Step

Find the source. Dry the floor, tank, bowl, supply line, and shutoff valve completely. Wait a few minutes, then press dry paper towel against each area to find where moisture first appears. Check whether water is on the floor, running into the bowl, or dripping from the tank. Water on the floor can travel from a higher connection, so do not assume the puddle marks the source.
Check for a tank-to-bowl leak. If the floor is dry but the toilet runs or refills without being flushed, the tank may be leaking into the bowl. Put a few drops of food coloring in the tank and wait 10 to 15 minutes without flushing. Color in the bowl points to a leaking flapper or flush-valve seal. Clean the bowl afterward.
Turn off the water for tank repairs. Turn the shutoff valve behind or beside the toilet clockwise by hand until it stops. Do not force a stuck valve; forcing it can break the valve or pipe. Flush to drain most of the tank, then use a sponge or towel to remove remaining water. Keep a bucket nearby.
Replace a worn flapper. Unhook the old flapper from the flush valve and disconnect its chain. Take it to a hardware store or match its shape and size to the toilet’s manual. Fit the new flapper flat over the valve opening, attach its ears or hooks, and reconnect the chain. Leave a little slack: a chain that is too tight can hold the flapper open, while excessive slack can tangle.
Adjust or replace the fill valve. If water keeps entering the overflow tube, check the float and water level. Adjust the float according to the valve instructions so the tank stops filling below the top of the overflow tube. If the valve will not shut off, is damaged, or continues to refill, replace it with a compatible valve. Follow its included directions and do not overtighten plastic fittings.
Inspect the supply connection. If moisture appears at the hose, shutoff valve, or tank connection, dry the area and check again to pinpoint the joint. A loose connection may need a slight, careful tightening with a wrench, but do not twist the valve or over-tighten. If the hose is cracked, corroded, or still leaking, replace it with a toilet supply line of the correct length and connection type. Follow the line’s instructions; do not apply tape or sealant unless its manufacturer specifies it.
Turn water back on and test. Open the shutoff valve slowly, watching the tank fill. Flush several times, then inspect the tank, supply line, valve, and floor with dry paper towel. Confirm that the tank stops filling at the correct level and that no water seeps out. Recheck after a short wait.
Handle a base leak differently. Water appearing around the base, especially after flushing, can mean the wax ring or another seal has failed. Stop using the toilet if water is escaping, and arrange repair. Replacing a wax ring requires removing and resetting the toilet; follow the toilet and seal instructions or hire a plumber. A loose toilet can damage the floor and worsen the leak.

Common Mistakes

Replacing parts before finding the leak: Water can run along the tank or hose and pool elsewhere. Dry everything and identify the first wet spot.
Forcing a shutoff valve or nut: Old valves and plastic fittings can crack. Stop if a valve will not turn easily or a connection starts to twist.
Setting the float too high: Water entering the overflow tube wastes water and can make the toilet seem to leak. Keep the fill level below the overflow opening as the valve instructions specify.
Leaving the flapper chain too tight: The flapper may not seal. Check that it closes fully after every flush.
Ignoring a base leak: Caulking around the base does not repair a failed seal and can conceal escaping water. Find and fix the source instead.

Tips

Photograph the tank setup before removing parts so you can compare the original arrangement.
Keep towels under the work area, and use a flashlight to inspect the back of the tank and the floor behind the bowl.
Use replacement parts that match the toilet or are explicitly listed as compatible. Follow the toilet or part maker’s instructions over general guidance.
If the toilet is not leaking onto the floor but runs intermittently, listen for refill sounds and use the food-coloring test before buying parts.
After repairs, check again later. A slow drip can be hard to see while the toilet is being used.

Troubleshooting

The toilet still runs after a new flapper: Check that the flapper matches the valve, sits evenly, and has a chain with enough slack. Mineral buildup or a damaged flush-valve seat can prevent a good seal; clean or replace the seat only if the toilet instructions allow it.

The tank keeps filling or water enters the overflow: Lower the float using the fill-valve instructions. If the valve does not stop filling or the overflow tube is damaged, replace the faulty part or call a plumber.

A connection leaks after tightening: Shut off the water and check whether the washer or supply line is damaged or misaligned. Replace the defective part rather than tightening harder. If the shutoff valve itself leaks, leave it alone and seek plumbing help.

Water appears at the base: Stop flushing and inspect whether the water may be coming from the supply line or tank above. If the base is the source, the toilet may need to be removed and resealed. Call a plumber if you cannot confidently reset it or if flooring is wet.

The shutoff valve will not close: Do not force it. If water is actively escaping and you cannot safely stop the supply, contact a plumber or building maintenance promptly. In a home, know where the main water shutoff is, but use it only if you can operate it safely.

Frequently Asked Questions

Why is my toilet leaking onto the floor?

Common sources include a supply-line connection, tank bolt or seal, shutoff valve, or the seal beneath the toilet. Dry the area and use paper towel to trace where water first appears; a leak at the base after flushing needs prompt attention.

Can a leaking toilet waste water without making a puddle?

Yes. A worn flapper can let tank water seep silently into the bowl. The food-coloring test can reveal this: color in the bowl without flushing indicates a tank-to-bowl leak.

Is it safe to use a toilet that leaks at the base?

It is best to stop using it until the source is identified. Repeated flushing can allow more water into the floor or subfloor, and the leak may indicate a failed seal.

Should I use plumber’s tape on toilet connections?

Only if the connection or part instructions specify it. Many toilet supply connections seal with a washer, and tape may interfere with that seal or encourage overtightening.

When should I call a plumber?

Call if a shutoff valve is stuck or leaking, a toilet or pipe is cracked, water is reaching the floor or ceiling below, or a base seal needs replacing and you are not comfortable removing the toilet.

Further reading: U.S. Environmental Protection Agency. Details can change, so check the official page for anything that matters to you. Spotted a mistake? Tell us. How we write an answer.