How to Install a Toilet Tank Gasket

What You'll Need
Toilet tank gasket kit, with washers and connecting bolts
Crescent-head adjustable wrench
Large flat-blade screwdriver
Sponges and terrycloth towels
Quilt or blanket padding for toilet tank and lid
Rust remover or WD-40 lubricant
Rubbing alcohol
Clean rags
A helper

A cone-shaped toilet tank gasket creates a watertight seal between the toilet tank and the toilet bowl, so water can flow quickly to flush the toilet. When the toilet tank gasket breaks down, and leaks will appear on the floor around the bowl and tank bolts. Use these tips and tools to do this job yourself.

Step 1: Shut Off Water Flow to the Toilet and Empty the Tank

Turn off the toilet water shutoff valve, fitted into the wall near the floor behind the toilet. Flush the toilet to clear it of water. Adjust the crescent-head adjustable wrench to fit the water supply line and disconnect it from the toilet tank. Place large towels on the floor behind the toilet bowl to absorb water splashes.

Step 2: Remove the Tank Lid and Dry the Tank

Lift the tank lid off carefully and set it on a quilt or blanket well away from your work area. Use sponges and more towels to dry the tank floor and walls completely.

Step 3: Loosen and Remove the Tank Bolts

With the large flat-bladed screwdriver, attempt to turn the tank bolts anti-clockwise to loosen and release them. If they are solidly rusted into place, apply rust remover and let it penetrate for 6 to 8 hours to remove rust and corrosion. Unscrew them with the screwdriver, releasing the nuts with the wrench.

Step 4: Remove the Toilet Tank and Gasket

The toilet tank weighs over 50 pounds, so if you are not able to lift it yourself, get a helper to lift the toilet tank from the bowl. Stand the tank upside down on towels and blankets away from the toilet bowl. Carefully extract the old gasket and rubber fragments. Wipe the tank hole with rubbing alcohol to remove all the old rubber bits.

Step 5: Insert the New Gasket and Bolts

Put the new toilet tank gasket inside the hole with the cone-shaped end facing outward. Lay the toilet tank flat to insert the bolts from inside. Place one rubber washer on each bolt directly under the head, and insert the bolts into the bolt holes. Place a second rubber washer on each bolt where they exit from the tank. Next, put the bolt's tightening nut on the bolt. The third rubber washer goes under the nut, with a metal washer below it.

Step 6: Reattach the Toilet Tank

Lift the toilet tank carefully and align it so the gasket goes into the hole on the toilet bowl back and the bolts fit into the toilet bowl. Shift and wiggle the tank carefully so everything lines up perfectly. Tighten the bolts slowly, alternating sides for correct and level fit. Set the toilet tank lid back on top of the tank.

Step 7: Restore the Water Supply

Reattach the water supply line, turn on the water flow valve and check for any leaking at the tank or the bowl for 48 hours.