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Can I Use Flex Seal on a Toilet Tank?

Don’t you just hate when your toilet tank is leaking? You don’t always have time, or money, to call in a plumber, right?

So, you want to fix your toilet tank as soon as possible. You may find yourself asking ‘Can I use flex seal on a toilet tank? Luckily for you, the answer is yes.

Let us delve deeper into this, shall we?

Flex Seal: What is it?

Before you call in a plumber and wait for them to fix your toilet tank, you can always use quick alternatives like Flex Seal. But what exactly is it? Just as the name might imply, this product is formulated to seal gaps, leaks, and cracks on different surfaces.

Of course, this is made possible by the liquid rubber sealant that creates a waterproof yet flexible barrier on any surface it is applied to.

Now, it is worth noting that Flex Seal is a line of products including aerosol sprays and liquid sealants. They are commonly used by DIYers for quick fixes and home repairs. What’s more, they can be used on different materials including concrete, fabric, plastic, wood, and metal.

Is Flex Seal Waterproof?

The biggest question you probably have at this moment is if Flex Seal is waterproof, and understandably so, because you are looking to fix a toilet tank. Flex Seal is waterproof and that’s because it creates a rubber-like malleable barrier that will not allow water to seep through when applied correctly. 

It adheres to different surfaces as we have previously mentioned. As such, it can effectively form a watertight seal that will prevent or reduce leaking albeit temporarily.

Now, while this product is waterproof, you want to keep in mind that its effectiveness will depend on various factors including surrounding conditions, the severity of the leak, and the surface. Of course, you would then want to follow user instructions for best results.

How Does the Flex Seal Spray Work?

At this point, you already know that the Flex Seal Spray functions by forming a rubberized and flexible barrier on surfaces. Here’s how to use it for best results.

Prepare the Surface

This goes without saying. Prep plays a major role in ensuring that your sealant is effective. As such, you want to clean the surface you want to apply your sealant. This eliminates any grease or dirt that may affect adhesion.

Shake the Can

When your can is sitting, chances are that all the good stuff collects at the bottom. To ensure that it mixes up well to give you proper adhesion, shake your can vigorously before spraying your surface.


Now that you are ready to apply your sealant, hold the can about eight inches away from the surface and spray in a steady back-and-forth motion. You may need to apply a few coats of the sealant depending on how bad your crack or gap is.  

If this is the case, give each coat time to dry before putting on the next one.

As soon as Flex Seal cures, it will form a rubberized seal that keeps water from leaking. Although it is not a permanent solution, it will certainly do a good job until you fix your problem permanently.

Is your Toilet Tank Cracked? How to Tell

Here are a few indicators that may suggest a cracked toilet tank:

Visible Cracks

Inspect the exterior of the toilet tank carefully. Look for any visible cracks or fractures on the surface. Cracks can vary in size and may be hairline cracks or more significant fractures.

Water Leakage

A common sign of a cracked toilet tank is water leakage. If you notice water pooling around the base of the toilet or on the floor, it could indicate a crack in the tank. Check for dampness or water stains around the tank area.

Constant Running Water

If the toilet tank is constantly refilling even when not in use, it might be a sign of a crack. A crack can cause water to continuously leak out, triggering the refill mechanism to compensate for the lost water.

Audible Hissing or Gurgling Sounds

Listen for any hissing or gurgling sounds coming from the toilet tank. These noises can be indicative of water escaping from a crack.

Fluctuating Water Levels

Observe the water level in the tank. If you notice the water level dropping unexpectedly or fluctuating without any flushing or water usage, it could suggest a crack.

Can Flex Seal be used on a Cracked Tank?

Flex Seal is designed to be used as a sealant. Therefore, it can be used to repair cracks in your tank. That said, you want to remember that this product will not offer a permanent solution especially if you are dealing with larger cracks.

Flex Seal Alternatives

So, what if you cannot get your hands on a can or tube of Flex Seal? Are there any substitute products you can use? Certainly! Here are some common alternatives that work the same as Flex Seal.

Pipe Repair Tape

This elastic product will clump around the surface you want to repair. It creates a watertight seal and is often used for temporary or emergency repairs. The tape adheres to itself and forms a flexible barrier.

Plumbing Epoxy

This product is exclusively designed to be used for plumbing repairs. It is designed to create a strong and durable seal on various surfaces, including metal and plastics. In that regard, it can be effective for sealing leaks in pipes, fixtures, and other plumbing components.

Epoxy Putty

Epoxy putty is a versatile and durable solution for sealing leaks. It consists of two components that need to be mixed together to activate the epoxy. Once mixed, it can be applied to the affected area and shaped as needed. Epoxy putty sets hard and provides a strong seal.