How to Fix a Cracked Toilet Tank Temporarily or Replace It

Stop the water first

The moment you notice a crack, shut off the water before doing anything else. The shut-off valve is usually on the wall or the floor below the tank. Turn it clockwise until it stops, then flush the toilet to empty most of the tank. Sponge and bucket the remaining water out. If the valve is seized or missing, plan to install a toilet shut-off valve before you do any repair.

Do not keep flushing a toilet with a cracked tank. Water that escapes through the china can soak the bathroom floor, the subfloor, and the ceiling below. EPA reports that household leaks can waste 180 gallons per week, and toilets are often the culprit.

Inspect the crack before sealing

Dry the crack and inspect it with a bright light. A hairline surface crack that is dry, not growing, and visible from the outside only can be treated as an emergency for a short period. A crack that is damp, that catches a fingernail, or that shows on both surfaces of the china is a structural break. Use a step-by-step inspection such as how to check a toilet tank for cracks before you decide.

Pay extra attention to cracks that start at a tank bolt hole. They are usually caused by over-tightened bolts, they tend to weep at the tank-to-bowl joint, and they get worse as the tank fills. This kind of failure is closely related to tank leaks at the bolts and should be treated as a replacement issue.

Temporary sealing options

For a temporary fix on a hairline crack, use a waterproof epoxy or a silicone sealant rated for plumbing and ceramics. Clean the area, dry it completely, and press the sealant into the crack. Smooth it flat with a putty knife or a gloved finger. Keep the tank empty while the seal cures, and understand that this is a stopgap, not a permanent repair.

Skip duct tape, plastic wrap, and ordinary exterior caulk. A full toilet tank is heavy, and the tank flexes slightly every time it fills and flushes. A weak patch can fail without warning and leave you with a wet floor. If you choose to seal, set a date to replace the tank or the toilet instead of treating the seal as the final fix.

When replacement is the right call

A toilet tank is a vitreous china fixture fired with the glaze as part of the piece. A structural crack cannot be welded or fused the way a metal part can. Once the china is broken through, the only reliable option is a new tank or a new toilet. The decision rule is simple: a cracked tank is a replace, not a repair situation once the crack is structural.

Replace the tank when the crack is leaking, when it runs through the full thickness of the china, when it is getting longer, or when water damage is already visible below the toilet. Replace it also if the crack starts at a bolt hole and the tank-to-bowl joint has begun to weep. A sudden tank failure can release the entire contents of the tank onto the floor.

If the toilet is old enough to be wasting water, think about replacing the whole unit rather than just the tank. EPA notes that older inefficient toilets can use as much as 6 gallons per flush, while WaterSense labeled toilets use 1.28 gallons per flush or less, 20 percent less than the current federal standard of 1.6 gallons per flush.

Swapping the tank on a two-piece toilet

Most residential toilets are two-piece designs with a separate tank bolted to the bowl, which makes a tank swap possible for a careful homeowner. Empty the tank, disconnect the supply line at the base of the tank, and remove the tank bolts from inside. Lift the tank straight up and set it on a padded surface so the rim does not chip.

For the full procedure, see how to replace a two-piece toilet tank. The job also involves installing new tank bolts and fitting a new tank-to-bowl gasket.

When the new tank is in place, tighten the bolts evenly and gently. Over-tightening is one of the most common causes of new cracks around the bolt holes. Reconnect the supply line, open the shut-off valve, and watch for drips around the bolts and the supply connection before returning the toilet to service.

Choosing a replacement toilet

If you replace the whole toilet instead of only the tank, you can solve several problems at once. Check the bowl for chips, inspect the wax ring and flange, and confirm the rough-in distance before buying. See how to measure the rough-in and how to install a toilet for the details.

The choice of replacement can affect household water use in a real way. EPA reports that the average American family uses more than 300 gallons of water per day at home, and roughly 70 percent of that happens indoors. Toilets are by far the main source of indoor water use, accounting for nearly 30 percent of an average home's indoor consumption. A WaterSense labeled toilet uses 1.28 gallons per flush or less, 20 percent less than the federal standard of 1.6 gallons per flush.

Some homeowners prefer a one-piece toilet after a tank crack because the tank and bowl are cast as one unit. That removes the tank-to-bowl joint and the bolts that can crack. Compare models in the best one-piece toilets guide. For a direct replacement with a separate tank, the best two-piece toilets guide is the right place to start.

What to pick for your use

Questions

Can I repair a cracked toilet tank permanently?

No permanent repair exists for a crack that goes through the china. Epoxy and silicone are temporary measures that can hold for a while, but the tank flexes each time it fills and flushes. Plan on a new tank or toilet for any structural crack.

How can I tell if a crack is serious?

A crack that is leaking, that you can feel from both surfaces of the china, that grows over time, or that starts at a tank bolt hole is serious. A crack that has already caused water stains on the floor or ceiling also means the tank should not stay in service.

Is it safe to use a toilet with a cracked tank?

Not for long. Keep the water shut off between uses, or use another bathroom until the tank is sealed or replaced. If the tank fails while you are away, the entire contents can end up on the floor.

Can I replace just the tank instead of the whole toilet?

Yes, if the toilet is a two-piece model and the bowl is in good condition. The replacement tank must suit the same bowl family and match the bolt spacing and gasket style. If the toilet is old or inefficient, replacing the whole unit is often simpler.

What tools do I need to swap a tank?

An adjustable wrench, a screwdriver, a bucket, a sponge, new tank bolts, and a new tank-to-bowl gasket. If the shut-off valve is rusted or the supply line is damaged, add those parts to the job.

When should I call a plumber?

Call a plumber if the shut-off valve is stuck, the supply pipe is corroded, the bowl is also damaged, or you are not comfortable lifting a china tank. If the leak is active and you cannot control it, turn off the water and get help quickly.