Why is water leaking around the bottom of my toilet tank?

A loose or corroded tank bolt is one of the most common causes. The rubber washer under the bolt head compresses over time and allows water to seep past. Tightening the bolt or replacing the washer usually stops the leak.

How many bolts does a standard toilet tank have?

Most standard toilets have two tank bolts, one on each side of the flush valve opening at the bottom of the tank. Some older or specialty models may have three, but two is by far the most common configuration.

Can I tighten toilet tank bolts without draining the tank?

You can attempt small adjustments without draining, but for any significant tightening or washer replacement you should shut off the water supply, flush to empty the tank, and then work on the bolts. This prevents water from dripping on you and gives you a clear view of the hardware.

What tools do I need to tighten a toilet tank bolt?

A large flat-head screwdriver to hold the bolt slot inside the tank, and a pair of adjustable pliers or a small socket wrench to tighten the nut underneath. A flashlight and a towel are also helpful.

How tight should toilet tank bolts be?

Snug but not over-tightened. Tighten until the tank sits firm and the washer seals against the porcelain, then stop. Over-tightening is the leading cause of cracked toilet tanks — porcelain does not flex and will crack under excessive bolt pressure.

When should I replace the tank bolts instead of just tightening them?

Replace the bolts if you see visible corrosion, if the nut spins without tightening (stripped threads), or if the rubber washers are visibly deteriorated or brittle. A full toilet tank bolt kit costs just a few dollars and is worth replacing proactively during any toilet repair.

How to Fix a Loose Toilet Tank Bolt: Step-by-Step Guide

A loose toilet tank bolt might seem like a minor annoyance, but it can lead to real water damage if left unchecked. The small leak that starts at the base of a loose bolt can drip steadily onto the floor, slowly damaging subfloor materials over weeks or months. Fortunately, tightening or replacing a toilet tank bolt is one of the simplest plumbing repairs a homeowner can tackle in under 30 minutes.

Understanding the Tank Bolt Assembly

The toilet tank sits on top of the bowl and is held down by two (sometimes three) bolts that pass through holes in the bottom of the tank and through the back of the bowl. Each bolt has a rubber gasket or washer on the inside of the tank, a rubber or plastic washer under the tank bottom, and a metal washer and nut underneath the bowl rim. A separate large rubber spud washer seals the flush valve opening between the tank and bowl.

Over time, rubber washers compress and harden, metal bolts corrode, and the assembly loosens — causing the tank to rock and water to leak.

What You Will Need

Large flat-head screwdriver
Adjustable pliers or channel-lock pliers
Toilet tank bolt replacement kit (bolts, washers, nuts)
Towels or a small bucket
Flashlight
Teflon tape (optional)

Step 1: Shut Off the Water Supply

Turn the shut-off valve on the wall behind the toilet clockwise until it stops. Flush the toilet to drain the tank completely. Use a towel to soak up any remaining water in the bottom of the tank before working on the bolts.

Step 2: Locate and Inspect the Bolts

Look inside the bottom of the tank to find the two bolt heads. They are typically brass or plastic and sit near the front of the tank bottom. Inspect them for corrosion, cracks, or deteriorated rubber washers. If the bolts look corroded or the rubber is hardened and cracked, plan to replace the entire assembly rather than just tighten.

Step 3: Tighten the Bolts

Hold the bolt head inside the tank stationary with your large flat-head screwdriver. From underneath the tank, use adjustable pliers to turn the nut clockwise — just a quarter to half turn at a time. Alternate between the two bolts to keep pressure even and prevent the tank from tilting. Check inside the tank periodically to make sure the washer is seating flat.

Stop tightening as soon as the tank feels solid. Do not force it further.

Step 4: Replace Corroded or Stripped Bolts

If the nut just spins without tightening, the threads are stripped and the bolts must be replaced. In some cases corroded bolts are difficult to remove — use penetrating oil and let it soak for 15 minutes before trying again. If the bolt still will not budge, use a small hacksaw or oscillating tool to cut it off between the nut and the bowl.

Install the new bolts from your toilet tank repair kit by:

Sliding a rubber washer onto each new bolt.
Dropping the bolt through the hole inside the tank, washer-side down.
On the underside of the tank, add a metal washer and hand-thread the nut.
Hold the bolt head with a screwdriver and snug the nut from below with pliers.

Step 5: Check and Replace the Spud Washer

While the tank is off (if you removed it), inspect the large rubber spud washer that seals between the tank and bowl. If it is cracked or compressed flat, replace it. A failed spud washer causes leaks at the tank-to-bowl joint regardless of how tight the bolts are. Replacement spud washers are inexpensive and easy to swap out.

Step 6: Restore Water and Test

Turn the shut-off valve back on and let the tank fill. Watch the base of the tank and the floor around the toilet closely for any sign of dripping. Dry the area first with a towel so you can spot even a small leak. If everything looks dry after a full flush cycle, the repair is complete.

Maintenance Tips

Check your toilet tank bolts once a year by gently rocking the tank side to side. Any movement is a sign the bolts need attention before a leak develops. Replacing rubber washers every 5 to 7 years as preventive maintenance is inexpensive and avoids the surprise of a leaking toilet tank.

⏰ PT2H 💰 $10–$50 🔧 Plunger, Drain snake or auger, Bucket, Rubber gloves, Plumber putty or wax ring

Shut Off the Water Supply
Turn the shut-off valve on the wall behind the toilet clockwise until it stops. Flush the toilet to drain the tank completely. Use a towel to soak up any remaining water in the bottom of the tank before working on the bolts.
Locate and Inspect the Bolts
Look inside the bottom of the tank to find the two bolt heads. They are typically brass or plastic and sit near the front of the tank bottom. Inspect them for corrosion, cracks, or deteriorated rubber washers.
Tighten the Bolts
Hold the bolt head inside the tank stationary with your large flat-head screwdriver. From underneath the tank, use adjustable pliers to turn the nut clockwise — just a quarter to half turn at a time.
Replace Corroded or Stripped Bolts
If the nut just spins without tightening, the threads are stripped and the bolts must be replaced. In some cases corroded bolts are difficult to remove — use penetrating oil and let it soak for 15 minutes before trying again.
Check and Replace the Spud Washer
While the tank is off (if you removed it), inspect the large rubber spud washer that seals between the tank and bowl. If it is cracked or compressed flat, replace it.
Restore Water and Test
Turn the shut-off valve back on and let the tank fill. Watch the base of the tank and the floor around the toilet closely for any sign of dripping. Dry the area first with a towel so you can spot even a small leak.