How to Fix a Leaky Toilet

🧰 Tools & Materials

Tools

• Adjustable wrench
• Channel-lock pliers
• Flathead screwdriver
• Phillips screwdriver
• Flashlight
• Small bucket or bowl
• Sponge
• Old towels or rags

Materials

The exact materials depend on where the toilet is leaking. You may need:

• Replacement toilet supply line
• Replacement fill valve, if needed
• Replacement tank bolts and rubber washers
• Tank-to-bowl gasket, if needed
• Toilet wax ring, if the leak is coming from the base

Signs Your Toilet Is Leaking

Some toilet leaks are obvious. Others only appear while the toilet is filling or flushing.

Common signs include:

• Water collecting around the base of the toilet
• Water dripping from the supply line
• Moisture underneath the toilet tank
• Water appearing between the tank and bowl
• A leak that only appears when you flush
• Water running down the outside of the bowl
• A toilet that rocks slightly when you sit on it
• Staining or damaged flooring around the toilet
• A damp ceiling below an upstairs bathroom

Before replacing anything, identify where the water is actually coming from. Several different toilet problems can leave water on the same area of the floor.

Before You Start

Dry the toilet and surrounding floor completely.

This is important. Water can travel along the outside of the tank, bowl, supply line, or floor before dripping somewhere completely different from the actual leak.

Once everything is dry, place a few pieces of dry toilet paper or paper towel around the most common leak points:

• Shut-off valve
• Supply-line connections
• Bottom of the toilet tank
• Tank bolts
• Tank-to-bowl connection
• Base of the toilet

Flush the toilet and watch closely.

You may need to flush it several times before the leak appears.

Run your fingers carefully along the outside of the tank and connections to find the highest point where you detect fresh water.

Also check for condensation. In a humid bathroom, cold water inside the tank can cause moisture to form on the outside and drip onto the floor. Condensation can look surprisingly similar to a plumbing leak.

💡 Pro Tip: Always trace the water upward. The place where water lands is not necessarily where the leak started.

Step 1: Check the Shut-Off Valve

Start at the wall or floor behind the toilet.

Dry the shut-off valve and the surrounding area completely.

Look around the valve stem, where the supply line attaches, and where the valve connects to the household plumbing.

Use a dry paper towel around each connection. Even a very small leak will leave a wet spot.

If water is leaking from the valve itself, the toilet shut-off valve may need repair or replacement.

Snug it gently with a wrench or pliers. Do not overtighten it.

If water is leaking from the valve itself, the shut-off valve may need repair or replacement.

What You Should See: The shut-off valve and surrounding connections should remain completely dry while the toilet fills.

If Yours Looks Different: Some toilets have older multi-turn shut-off valves while others have quarter-turn valves. The design may differ, but the same basic test applies: dry everything and identify exactly where fresh water first appears.

Step 2: Check the Supply Line

Follow the flexible supply line from the shut-off valve to the bottom of the toilet tank.

Check both ends for moisture.

Flush the toilet so the fill valve opens and water flows through the supply line.

Leaks are often easier to spot while the toilet is actively refilling.

If one of the connections is slightly loose, tighten it gently.

If the braided hose is damaged, kinked, corroded, or leaking from the hose itself, replace the entire supply line rather than trying to repair it.

What You Should See: The supply line and both connections should remain completely dry while the toilet fills.

💡 Pro Tip: If you replace the supply line, take the old one with you when buying the replacement. It makes matching the connection sizes and choosing the correct length much easier.

Step 3: Inspect the Tank Bolts

Look underneath the toilet tank where it attaches to the bowl.

Most two-piece toilets have bolts passing through the bottom of the tank.

Use a flashlight to check around each bolt.

Water may drip directly from a bolt or run along the underside of the tank before falling onto the floor.

Inside the tank, rubber washers seal around these bolts. As the washers age, they can harden, crack, or stop sealing properly.

If a bolt is only slightly loose, it may need gentle tightening.

Hold the bolt inside the tank with a screwdriver while carefully tightening the nut underneath.

Tighten each side gradually rather than fully tightening one bolt at a time.

Do not crank down on the bolts. Excessive pressure can crack the porcelain tank.

If tightening does not stop the leak, replace the tank bolts and rubber washers.

What You Should See: After flushing and refilling, the underside of the tank around both bolts should remain dry.

If Yours Looks Different: One-piece toilets do not have a separate tank-to-bowl connection, so you may not see exposed tank bolts underneath.

Step 4: Check the Tank-to-Bowl Gasket

If water appears between the tank and bowl, particularly during a flush, inspect the large gasket between them.

This gasket seals the opening where water leaves the tank and enters the bowl.

Dry the area thoroughly and flush again.

Watch directly underneath the center of the tank.

If water appears there only while flushing, the tank-to-bowl gasket may be deteriorated or improperly seated.

Before replacing it, gently check whether the tank mounting hardware is evenly snug.

The tank should feel secure without rocking excessively.

If the gasket needs replacement, shut off the water, flush the toilet, sponge the remaining water from the tank, disconnect the supply line, and remove the tank.

Replace the gasket with one designed for your toilet.

Reinstall the tank and tighten the bolts gradually, alternating from side to side.

What You Should See: The tank should sit securely on the bowl and the connection underneath should remain dry through several flushes.

If Yours Looks Different: Tank-to-bowl gaskets are not universal. Their diameter, thickness, and shape can vary between toilet models. Match the old gasket or use the toilet’s model information when buying a replacement.

Step 5: Check for Water Running Down the Tank or Bowl

Before assuming the leak is underneath the toilet, inspect the entire exterior.

Dry the tank and bowl.

Flush the toilet and watch for water beginning higher up.

Check:

• Tank lid area
• Flush handle opening
• Tank bolts
• Supply connection underneath the tank
• Tank-to-bowl connection
• Exterior surface of the tank

Also look for condensation.

If the entire outside of the tank feels damp rather than one specific connection becoming wet, condensation may be the culprit.

What You Should See: A plumbing leak usually creates a specific wet path beginning at a connection or seal. Condensation tends to create widespread moisture across the cold surface of the tank.

Step 6: Check for a Leak at the Base

If every connection above the floor remains dry but water appears around the bottom of the toilet after flushing, the wax ring becomes a likely suspect.

If the seal has failed, follow our guide on How to Replace a Toilet Wax Ring for the full repair process.

Dry the floor around the toilet completely.

Place dry toilet paper around the base.

Flush several times while watching closely.

Water from a failed wax ring often appears near the base shortly after a flush.

Next, gently try to rock the toilet from side to side.

The toilet should feel solid.

If it moves, the mounting bolts may be loose, the toilet may not be properly supported, or the flange underneath may have a problem.

Do not simply caulk over a leaking toilet base. Caulk can hide the water without fixing the failed seal underneath.

What You Should See: The toilet should remain solid against the floor, and no fresh water should appear around the base after flushing.

If Yours Looks Different: If water appears around the base even when the toilet has not recently been flushed, trace the water carefully again. A leaking supply line, tank connection, or condensation can run down the toilet and collect at the base.

💡 Pro Tip: A base leak that appears specifically after flushing is one of the strongest clues that the wax ring or toilet-to-flange connection needs attention.

Step 7: Replace the Failed Part

Once you have identified the source, replace only the component responsible for the leak.

Depending on what you found, that may mean:

• Replacing the supply line
• Replacing leaking tank bolts and washers
• Replacing the tank-to-bowl gasket
• Replacing the wax ring
• Replacing the toilet shut-off valve

If the problem is inside the tank rather than an external leak, How to Replace a Toilet Fill Valve and How to Fix a Running Toilet cover two of the most common internal toilet problems.

Do not replace several unrelated parts simply because water appeared on the floor.

If you need to remove the toilet to replace the wax ring, inspect the flange while the toilet is off.

If you need to remove and reinstall the entire fixture, see How to Replace a Toilet for the complete step-by-step process.

A cracked, badly corroded, or loose flange can prevent a new wax ring from sealing correctly.

Likewise, if you remove the tank, inspect the bolts, washers, and gasket together while they are accessible.

Step 8: Test the Toilet for Leaks

Dry every repaired connection and the surrounding floor before testing.

Slowly turn the water supply back on if you shut it off.

Allow the tank to fill completely.

Inspect the supply line, shut-off valve, tank bolts, and underside of the tank before flushing.

If everything remains dry, flush the toilet.

Watch every area you disturbed.

Flush the toilet three to five times and inspect again.

If you repaired a leak at the base, place dry toilet paper around the toilet and check it after each flush.

If you repaired a tank or supply connection, wipe around it with a dry paper towel.

What You Should See: Every connection should remain completely dry, the toilet should sit firmly on the floor, and no water should appear around the base during or after flushing.

If Something Goes Wrong

Problem: Water still appears around the toilet base

Dry everything again and determine whether the water is actually coming from underneath the toilet. A tank bolt, supply connection, or condensation can send water down the bowl and make a good wax ring look like it is leaking.

If the water definitely emerges from beneath the toilet after flushing, the wax ring may not be sealing correctly.

Problem: A new wax ring still leaks

The toilet may not be sitting squarely on the flange, the flange may be damaged or too low, or the toilet may be rocking.

Remove the toilet and inspect the flange rather than installing another wax ring without finding the cause.

Problem: The tank leaks after replacing the bolts

Make sure the rubber washers are positioned correctly inside the tank and that the bolts are tightened evenly.

If the tank rocks, gradually tighten each side until it is stable. Do not overtighten the hardware to compensate for a poorly seated gasket.

Problem: The tank-to-bowl connection still leaks

The gasket may be crooked, incorrectly sized, or incompatible with the toilet.

Remove the tank and verify that the gasket sits evenly around the flush-valve outlet.

Problem: The supply connection drips after tightening

Disconnect it and inspect the connection.

A damaged washer, worn supply line, or cross-threaded fitting will not reliably stop leaking simply by tightening it harder.

Problem: The shut-off valve starts leaking when you operate it

Older shut-off valves can begin leaking around the stem after being disturbed. A minor stem leak may sometimes be corrected by gently tightening the packing nut.

If the valve itself is corroded or continues leaking, replacement may be necessary.

Problem: The toilet rocks after replacing the wax ring

Do not keep tightening the closet bolts in an attempt to pull the toilet flat against an uneven floor.

The toilet may need proper toilet shims so it sits firmly without rocking. Excessive bolt pressure can crack the porcelain.

Problem: The floor around the toilet feels soft

Stop using the toilet until the area is investigated.

A long-term leak may have damaged the subfloor. Installing another wax ring without addressing damaged flooring or a loose flange may not provide a lasting repair.

🛑 Common Mistakes to Avoid

• Assuming water at the base automatically means the wax ring has failed
• Troubleshooting before completely drying the toilet and floor
• Overtightening tank bolts or closet bolts against porcelain
• Tightening a leaking supply connection harder instead of inspecting its washer
• Replacing multiple parts without first locating the source of the leak
• Reusing deteriorated tank bolt washers
• Installing the wrong tank-to-bowl gasket
• Caulking over an active leak at the toilet base
• Installing a new wax ring without checking for a damaged flange
• Ignoring a toilet that rocks on the floor
• Continuing to use a toilet when the surrounding floor feels soft or damaged

❓ FAQs

Why is my toilet leaking onto the floor?

Common sources include the supply line, shut-off valve, tank bolts, tank-to-bowl gasket, condensation, or the wax ring underneath the toilet. Dry everything first and trace the water to its highest wet point.

Does water around the base always mean the wax ring is bad?

No. Water leaking higher on the toilet can run down the bowl and collect around the base. A wax ring becomes more likely when water specifically appears from underneath the toilet after flushing.

Can I keep using a toilet with a small leak?

It is better to identify and repair the leak promptly. Even a small amount of water can damage flooring, subflooring, trim, or the ceiling below the bathroom over time.

Why does my toilet only leak when I flush?

A leak that appears during flushing often points toward the tank-to-bowl gasket or wax ring because those connections experience water flow during the flush.

Can toilet tank bolts be tightened to stop a leak?

Sometimes a slightly loose bolt can be gently tightened. However, overtightening can crack the porcelain. If the rubber washer has deteriorated, replacing the bolt and washer is the better repair.

How do I know if my toilet wax ring is leaking?

Water appearing from beneath the toilet shortly after flushing, especially when all above-floor connections remain dry, is a common sign. A rocking toilet can also contribute to wax-ring failure.

Should a toilet move at all when I sit on it?

No. A properly installed toilet should sit firmly against the floor without rocking. Movement can damage the wax seal and may indicate an uneven floor, loose hardware, or flange problem.

Can condensation make it look like my toilet is leaking?

Yes. Cold tank water combined with warm, humid bathroom air can create enough condensation to drip onto the floor. Condensation usually leaves widespread moisture on the tank rather than a single wet connection.

📞 When to Call a Professional

Finding and repairing a leaking supply line, tank bolt, gasket, or wax ring can all be reasonable DIY projects once you have correctly identified the source.

Consider calling a plumber if:

• You cannot determine where the water is coming from.
• The toilet continues leaking after the suspected component has been replaced.
• The toilet flange is cracked, badly corroded, loose, or significantly below the finished floor.
• The shut-off valve will not close or begins leaking significantly.
• The toilet or tank porcelain is cracked.
• The toilet repeatedly rocks even after proper adjustment.
• The flooring around the toilet feels soft or damaged.
• Water has reached the ceiling or room below.
• You discover significant subfloor damage after removing the toilet.

At that point, fixing the visible leak may only be part of the repair. The flange, flooring, or plumbing underneath the toilet may also need attention.

Related DIY Guides

• How to Replace a Toilet
• How to Replace a Toilet Wax Ring
• How to Replace a Toilet Shut-Off Valve
• How to Replace a Toilet Fill Valve
• How to Fix a Running Toilet