Cracked ceramic toilets need immediate repair to prevent further deterioration. You can repair the toilet yourself with a few household tools and the correct sealant, which you can purchase from a hardware store or home and garden shop.
Screw the water valve at the bottom left or right side of the toilet all the way clockwise. Flush the toilet.
Moisten a sponge in hot water. Wash the crack and the surrounding area with the sponge. Dry the crack and the surrounding area with a dry soft cloth.
Dribble water from the sponge into the crack. Screw the grinding pad on the end of your portable drill's drill bit. Set the power level switch to low.
Press the trigger of the portable drill. Apply an edge of the grinding pad to the crack. Press down on the pad as you move along the length of the crack. Repeat this procedure in a back and forth motion for 20 seconds before lifting the pad off.
Release the trigger on the drill and wipe the crack and the surrounding area with a damp soft cloth. Inspect the crack to see if its edges are smooth. Repeat the entire procedure if the edged look jagged. Otherwise, wipe the crack and the surrounding area with a dry soft cloth.
Apply clear epoxy sealant to the length of the crack. Stop applying the sealant when it overfills the crack and rises above the ceramic surface. Trowel the sealant across the length of the crack with a wooden craft stick. Let the sealant set for no less than eight hours before continuing the repair.
Sand the surface of the crack with rough-grit sandpaper for two minutes before switching to fine-grit sandpaper. Stop sanding when the surface is smooth to the touch. Wash the crack and the surrounding area with a dampened sponge.
Apply acetone to the edge of a soft cloth. Place the edge of the cloth against the left side of where the crack was. Press down on the cloth as you push it across the length of the crack. Throw the cloth in the trash.
Wipe the area where the crack was with the edge of a cloth. Let the acetone dry for a few minutes before applying a three-second spray of ceramic surface refinishing spray. Wait five minutes and then apply a five-second spray of ceramic surface repair spray. Let the toilet sit unattended for a day before screwing the water valve all the way clockwise.
Wear protective eyeglasses when sanding. Also, wear work gloves to protect your hands from the chemicals.
Improper ventilation during repair can lead to headaches due to chemical fumes.