Flex Seal Review & How To Seal and Stop Leaks Fast!

BY El Hosni, MAY 27, 2015 11:00 AM

Flex Seal Review Summary

Product Name:

Flex Seal 

Product Type:

Flex Seal




With leaking roofs, windows, pipes or gutters causing potentially hundreds or thousands of pounds worth of destruction, solutions like Flex Seal are an incredibly cost-effective prevention tool for homeowners worried about water damage or working with tight budgets.

This liquid rubber substance is an incredibly popular DIY product that can seal leaks, holes and cracks and provide a waterproof barrier that lasts for years - but many are asking whether it really works, and if it's as good as the hype suggests. We take a look at the ins and outs of Flex Seal to find out exactly what it has to offer.


Flex Seal Review

What is Flex Seal made out of?

Flex Seal is made from a very thick, mastic resin, among several other ingredients. To put it simply, it is a liquid rubber, but can be found in two different formats - in an aerosol can and in a thick, paint-like liquid. The formulation of Flex Seal differs slightly in each of these two formats, but the highly durable and waterproof resin ingredient ensures that each one provides a durable, watertight seal when the substance dries.

Although being waterproof is its most important feature, Flex Seal has been carefully formulated in order to be as convenient as possible to use and to offer excellent longevity against the elements. It won't melt, sag or drip during hot temperatures, or crack or peel in the freezing cold. Once dried, it remains pliable and flexible, it deadens noise, stops vibrations, and is even resistant to mildew and UV.Due to Flex Seal's versatile liquid form, it can easily seep into holes and cracks to provide thorough coverage and sealing even on very uneven surfaces.

Basically, it is a liquid rubber substance and has all the useful properties you would expect from rubber in the convenient format of a liquid.

How To Seal and Stop Leaks Fast?

The beauty of Flex Seal is that it has a really wide variety of applications, making it a handy DIY product to have around the house. Ultimately, it is designed to provide a watertight rubberised seal, so it can be used in any situation in which you want an area to be protected against leaks or water damage.

For example, you could fix holes and cracks in water pipes, hoses or guttering with Flex Seal, or apply it around window trims to prevent water damage during wet weather. It could be applied to walls in areas in which condensation is common to prevent damp, or, since it helps to deaden sound, it could be applied to floors to minimise noise. It could even be applied to wood fences or outdoor furniture to protect the wood from water damage.

Flex Seal is suitable for use on almost any surface you could imagine, including:

  • Metal
  • Wood
  • Concrete
  • Tile
  • Porcelain
  • Masonry
  • Cement
  • Dry wall
  • Rubber
  • Fabric
  • Glass
  • Aluminium
  • Plastic
  • Vinyl

When using Flex Seal indoors, it's important to ensure the area you're working in is well ventilated, so open all doors and windows before you start and leave open during application and while Flex Seal is drying. It is also advisable to wear protective clothing, particularly when using the aerosol variety, to avoid ruining clothes from accidental contact with the substance.

To get the best results, you should apply Flex Seal evenly using a sweeping motion, and to cover an area just slightly larger than that which you want to make watertight. So, if you need to seal a crack in a pipe for example, you should ensure that Flex Seal covers the entire crack and a reasonable area around it. To achieve a smooth finish, you should feather the edges to achieve a slightly thinner coat around the outside of the cracked area.

How long does it take Flex Seal to dry?

The drying time of Flex Seal greatly depends on the thickness of the coating applied, as well as the temperature and humidity of the environment it was applied in. Usually, it is dry to the touch within just two or three hours, but it takes a full 24 hours for the substance to completely cure and be fully waterproof.

Humid and very warm environments can make it take longer to dry, as can very cold conditions. Flex Seal gets stronger with time, so if at first you're worried that it feels too soft and pliable even after curing for 24 hours, you've no need to worry as it will only become stronger as the days go by.Depending on the reason for you using Flex Seal, you may find it necessary to apply multiple coats.

To achieve the best, most durable results, it is usually a good idea to apply several thin layers, letting each one dry completely before applying the next. This is particularly important for deep holes or cracks that you want to seal; although it's tempting to apply a thick layer in the deeper crevices, thin layers which you leave to dry separately will provide you with a more even and much stronger finished result.

Can you use Flex Seal on a wet surface?

Flex Seal can be applied to wet surfaces, which makes it an excellent sealant choice in emergency scenarios such as burst pipes in which you may not have time to ensure a surface is completely dry before fixing the leak. It's important to be aware though that Flex Seal does tend to take longer to dry when applied to wet surfaces, so you may have to wait longer before applying a second layer than if you were to make the area completely dry.

For the best results, Flex Seal should be applied to clean and dry surfaces, but if this isn't possible then don't worry too much - just make sure the area is as clean as possible and you should still achieve great results. Flex Seal is often used to seal leaky tiled roofs or windows, and in these instances it's important to note that very strong rain may wash some of the substance away if it is not completely dry.

If you've noticed a leak during wet weather, Flex Seal is still an excellent emergency solution, as it will dry despite the wet conditions. However, for the best results and to minimise the need for repeat applications, try to avoid applying it in very heavy rain and check the forecast to ensure that a strong rainstorm isn't on its way.

Is Flex Seal paintable?

Once Flex Seal is completely cured (24 hours) it can be painted any colour you wish. This is ideal for when you're treating areas that are visible in the home to ensure that repair work isn't obvious. For the best results, a latex-based paint is usually the most suitable option, but oil-based paint also works well. Often, though, it's best to leave Flex Seal to cure for longer than 24 hours - sometimes up to a week - to ensure that it becomes firm enough for oil-based paints to properly coat the Flex Seal surface.

Flex Seal

Does Flex Seal really work?

Over the years, Flex Seal has had thousands of happy customers who are genuinely satisfied with the results that Flex Seal creates, so it's safe to say that it really does work. A liquid rubber coating is a simple but incredibly effective idea, and the careful formulation of Flex Seal ensures that if offers incredible durability whilst being quick to dry and with no risk of it dropping or melting out of shape in future. It is this that makes it such an effective and popular product for homeowners who want a quick, convenient and long-lasting solution that really works.

Where to buy Flex Seal?

Flex Seal can be purchased from a wide variety of online stores and DIY stores for affordable prices. To ensure that you get the very best value for money, be sure to look out for multi-buy offers which let you get your hands on more Flex Seal for less - this is particularly handy for those who have big projects in mind, or those who simply want to stock up for emergencies or general DIY.Approve and download Or ask for changes!

What are the pros and cons of Flex Seal?

With a wide variety of applications and its strong, durable nature, Flex Seal has plenty going for it - but it's not completely without downsides. Let's take a look at the full list of pros and cons.


The Pros:
  • It's affordable: Flex Seal isn't a product that will break the bank and it has a really wide range of uses, so it's one of those inexpensive items that can be in every toolkit for those just-in-case moments. If you have a specific project in mind for Flex Seal and are unsure if it's the right tool for the job, the affordable price tag means you can just go ahead and give it a try with very little to lose. For leaky gutters, pipes or roofs, all of which can be very expensive to replace, it's a really inexpensive solution that will save you money and a great deal of time.
  • It can be applied to wet surfaces: Many sealants and resins require complete dry, clean surfaces in order to work at their best, but Flex Seal can be applied to wet surfaces and, although it may take a little longer to dry, will still give brilliant results. This means that you don't have to worry about waiting for perfectly dry weather before doing work outside, and you can quickly and easily fix things like leaky gutters in the middle of a light shower.
  • It takes a few hours to dry: Some sealants and resins seem to take forever to dry, but Flex Seal is formulated to be dry to the touch in just a few hours. This means that big projects, such as sealing an entire floor, can be completed within just one day or weekend, depending on the number of layers needed to complete the project. Plus, with application being so incredibly quick and easy, particularly when using the aerosol variety, the amount of work hours spent on a project is kept to a minimum.
  • It's convenient: Flex Seal is a really easy and convenient solution to a wide range of household problems. Applying it is by no means difficult and even those with little to no prior DIY experience could easily use the product to overcome problems which may at first seem very difficult to fix. For things like leaking roofs, which can cause significant water damage if left untreated, Flex Seal is a convenient solution that can avoid the need for pricey and complex roof repairs.
The Cons:
  • It can't be used in very heavy rains: Flex Seal can be used in wet conditions, but very strong rains may wash it away while it's still wet. This means that, if you've noticed a leak in your roof during a very heavy storm, you won't be able to get up there to fix it right away, but instead will have to deal with the incoming water until the rain eases up enough to get to work with Flex Seal.
  • It takes a few hours to dry: Yes, the drying time can be both a pro and con, depending on what it is you need Flex Seal for. For example, if you urgently need to fix a burst pipe, the two to three-hour wait time between coats could be very frustrating, and it may be quicker to simply replace the entire section of pipe. However, the latter would of course be more complex and more costly, particularly if you have to hire a plumber to do the work. Which leads us into the next pro...

Flex Seal Review: Videos & Testimonials

Flex Seal spray

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Flex Seal Benefits

  • Easy to use, portable, aerosol spray
  • Seeps into cracks and holes
  • Dries to a watertight, flexible, rubberized coating
  • Stays flexible and pliable, lasts for years
  • Protects surfaces from corrosion
  • Once dry, can be painted any color