How to repair a cracked toilet tank


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So, you walk into your bathroom, and now you have noticed that your toilet tank has cracked, yikes! A cracked toilet tank is a complicated issue because, depending on the severity of the crack, a toilet might even be leaking or be completely unusable.

It is essential to assess if the toilet tank can be repaired in the first place and act accordingly on time to avoid further damage. If it cannot be repaired or fixing it seems to be too complicated, then you might just be better off buying a new toilet or calling your plumber.

A rule of thumb is that cracks that are generally less than1/16 of an inch in width can attempt to be repaired. Cracks under this width are considered hairline cracks. If you are unsure, then call your plumber.

What causes a toilet tank to crack?

Accidents impacting the toilet tank or when repairing

Well, you know that there is a cracked toilet tank for no apparent reason. What might have happened here? Most toilets on households are made of porcelain, which can be somewhat fragile to any sort of impact.

For example, if an object hits the toilet tank because it was dropped, like a hair dryer, then this might cause a hairline crack (a crack that tends to be less than 1/16 of an inch or 1mm in width but might still cause some leaking).

Although sometimes hairline cracks can be more of a cosmetic issue, when it comes to toilet tanks, it is essential to get them fixed since they contain water; and it might leak. If the crack is repairable, fixing it would prevent leakage or further water damage. Sometimes if cracks are left unattended, they will just keep on growing.

Another common reason for cracks in the tank is when they are impacted when users attempt to put the lid back in place due to repairs or manipulating the fill valve. Make sure you remember this and put the lid back in place carefully after you fix your toilet tank to avoid further rupture.

Other repairs or installations on the toilet can cause it to crack. If a part is being installed, accidents might happen, where bolts are tightened too hard, or tools hit the tank in some way. Be careful when working on toilets, as porcelain is fragile.


Porcelain can be more susceptible to cracks over the years, as the material naturally deteriorates over time, making it easier for it to break. When aging is the issue, even changes in temperature between the water in the tank and the environment might cause a crack. If your toilet is old, then it might just be time to replace it altogether, instead of attempting to repair it.

Repair Instructions

What you need:

Waterproof Epoxy

-Putty Knife

-Piece of Cloth

Caulking gun (Optional)

Step 1. Draining the toilet tank.

Since you are most likely going to be using sealants that have to dry out, you want to avoid any water in the area you are going to be working in. Do this by closing the water supply. Next to the toilet on its lower part, there should be a valve or a lever you can close. Turn it clockwise to cut the water supply. Then, flush the toilet, so the water is drained.

Step 2. Dry out all parts of the toilet tank.

Use a piece of cloth to dry the tank out. Pass it on both the inside part of the tank and the outside. Make sure that there is no water left, and focus mainly on the area where the crack is located. Also, clean the area in which you are going to work on, there should not be any dust around.

Step 3. Apply the Epoxy mix to the crack.

The waterproof epoxy will prevent the leaking and the crack from expanding. You can either use a caulking gun or just apply it with a putty knife, making sure you cover the cracks entirely. If you are using a putty knife, then purchase an epoxy product that contains two parts that you have to mix for a blend that will ultimately seal the tank (the manufacturer will have more information on this process on the label).

Once mixed, the product must be used as soon as possible, as a chemical reaction begins to harden the sealant. Apply the mix to the crack, spreading it evenly and making sure that the blend gets in between the rupture.

If you have a caulking gun you will have to purchase an epoxy tube that fits the gun. Apply the mix along the crack and spread it evenly with the putty knife.

Step 4. Allow the sealant to dry out

To be safe, leave the epoxy to dry overnight. Check on the next day that the product got to all parts of the crack.

Step 5. Refill Tank.

Open up the water supply by turning the valve counterclockwise. Check that there is no dripping or water near the repair area.

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