Rust-Oleum Leak Seal Vs Flex Seal: Which is Superior?

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A surprise water leak can quickly become a catastrophic problem.

Usually, a leak isn’t spotted until it’s been raining and suddenly there’s water streaming down the walls or a tell-tale drip…drip…drip from the ceiling of the RV or campervan.

Invariably, you’re off-grid camping at the time or, at the very least, away from a repair shop.

To deal with the leak and prevent it from getting any worse, it’s necessary to perform a rapid temporary solution to stop further leakage. This is where either Rust-Oleum Leak Seal or Flex Seal spray products come into play.

It’s smart to have a bottle or can of these adhesive products stored away for water ingress issues. This allows you to leap into action and stop the moisture from becoming worse. The last thing you need is mildew developing because of it.

Which product is the best one to sort out leaks and seal them quickly?

Rust-Oleum Leak Seal Vs Flex Seal – Here are the Basics

As a spray-on solution from a can or a bottle in liquid form, both Flex Seal and Rust-Oleum Leak Seal can seal a gap, hole, or crack successfully in a modest amount of time.

When miles away from an RV repairer in a distant town, either product is a true lifesaver.

What Are Flex Seal and Leak Seal?

Both products in spray form are a type of rubber-coated paint. They will adhere to many types of surfaces including metal, wood, plastic, and more.

Designed as a utility coating, both will cover a lap sealant like the popular Dicor one too. However, it will not work successfully with silicone-based adhesives, which is the main exception to look out for.

Fundamental Differences Between the Two Products

Is Rustoleum Leak Seal the same as Flex Seal? No, not exactly but they’re often used for similar or the same purposes.

Both Flex Seal and Leak Seal are “rubber in a spray can” products. So, instead of always needing a pot of rubberized paint and a paint roller or brush to hand, the spray is more convenient.

Leak Seal sprays on like paint, rather than a rubber coating. Even to touch it, it feels and behaves like paint too. Some people even refer to it as, “Leak Seal paint”.  Indeed, anyone who’s used to painting a wall will be comfortable with the finish. Even if you touch it with your finger, it will behave as you’d expect.

Flex Seal is a little bit thicker in consistency. It behaves like a rubber texture even when sprayed on. It also takes on that appearance too. If you happen to touch it with your finger, it won’t be an even spread of material over your fingertip (and it’ll be harder to remove later too).

Here’s the Rust-Oleum Leak Seal Spray in its 11-ounce version. It’s a Clear color (other colors are available) and as a convenient two-pack:

Rust-Oleum LeakSeal Flexible Rubber Coating Spray, 11 oz (265495-2PK) – Clear (2 Pack)

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Also, here is the Flex Seal Spray sealant in a 14 oz, Black color (other colors are available). It’s provided in a two-pack, but other combinations are possible including being sold individually:


Flex Seal Spray Rubber Sealant Coating, 14-oz – Black (2 Pack)

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Repair Possibilities for Leak Seal and Flex Seal?

There are different repair possibilities depending on whether you’re using Leak Seal or Flex Seal spray products.

Sure, you can ask, “Does Flex Seal work?” It does… but depends on how you apply it and under what conditions. Generally, though, we confirm that it works well.  

Below, we run through a few possible repair options when using spray-on or liquid rubber paint solutions:

Flex Seal or Leak Seal on an RV Roof

We previously wrote about using Flex Seal on an RV roof. However, both Leak Seal and Flex Seal can perform roof repairs.

The idea of using a rubber sealant on the RV roof is to prepare the surface, so it’s ready for the rubber-in-a-can solution. Both rubber sealants do require time to cure fully. Because of this, it’s always a good idea to cover the area being worked on.

Whilst both Leak Seal and Flex Seal may be applied on wet surfaces and cured on those surfaces, they don’t work as well or as quickly in wet or moist conditions. Therefore, it’s a good idea to perform the repair work, especially on an RV roof, during a drier season or under a tarp cover.

Leak Seal is likely to dry a little faster and finish curing quicker than Flex Seal. This usually is not dependent on the type of material the rubberized solution is being sprayed on. As such, Rustoleum Leak Seal is an effective Flex Seal alternative.

Read Also: Can I Use Flex Seal on My RV Roof?

Rust-Oleum LeakSeal Flexible Rubber Coating Spray, 12 oz (265494-2PK) – Black (2 Pack)

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Flex Seal Over Rust? Should You Attempt It?

Covering an area of rust on metal with a spray-on or liquid solution like Flex Seal is like papering over the cracks. Rust-oleum Leak Seal is no better than Flex Seal in this respect.

Whilst it could be a fast, temporary solution, it will need to be removed later to perform a proper fix which is just making two jobs out of one. It’s also worth noting that adding Flex Seal over rusty metal will not prevent the rust from continuing to spread.

Instead, remove the rust by using a rust removal treatment. Then it’s possible to use a rubber spray or liquid solution such as Flex Seal to cover any gaps and seal them up.

Cover Caulking for a Stronger or Repaired Seal?

Various rubber sealing products can be successfully sprayed over traditional caulking and provide a sufficient seal. If you’re unable to purchase caulking in your current location and it’s already cracked, then a rubber sealant can provide a fast result.

With that said, some caulking ingredients are made from silicone. For a van lifer or an RV owner, it’s generally a bad idea to use silicone for caulking because it prevents using a spray-on rubber sealant at a future time.

It’s never good to limit your repair options!

Leak Seal or Flex Seal Over Silicone?

Both Leak Seal and Flex Seal aren’t cooperative with silicone.

When it comes to Flex Seal vs Silicone, it’s one or the other. If you start using silicone anywhere on your RV or camper van, it will make any rubberized adhesive solution ineffective.

The reason is simply that both rubber paint products aren’t designed to adhere successfully to silicone. Therefore, it’s an either-or situation here.

Color Choices for Rubber Spray Adhesives

Leak Seal Spray is available in many colors. These include yellow, clear, green, brown, almond, and others. With that said, by far the most commonly available are black and white.

Flex Seal Liquid Spray is available in either black, white, or clear colors.

Also, it should be noted that some colors may be limited to certain sizes.

How Much Spray Solution is Required? Let’s Talk Sizes

Depending on Flex Seal or Leak Seal, they each come in different size spray can configurations. Therefore, it’s a little like comparing apples to oranges.

As a useful guide, an 11-ounce can of Rust-Oleum Leak Spray match a surface area of approximately 8.8 feet. For a 14-ounce spray can of Flex Seal, plan for approximately 11 feet of coverage.

Of course, it depends entirely on how thickly the spray is applied, so your mileage may vary (YMMV).

A rule of thumb is to divide the ounce weight by 1.25 for a rough number of feet it might be used on before the product is fully depleted.

Currently, Leak Seal in spray version is sold in 11-ounce and 12-ounce versions. Flex Seal in its spray version is sold in both 14-ounce and 17-ounce versions. This may change in the future.

Read Also: How Often Should You Seal Your RV Roof?

Flex Seal and Leak Seal Cure Time

The cure time required for the spray versions of Leak Seal and Flex Seal varies depending mostly on the atmospheric or indoor conditions, the surface it’s being applied to, and what volume of spray solution is used. The liquid versions of each are not faster for curing.

Applying the spray can at least 9 inches above the surface to be sprayed on (and sometimes as much as 14 inches away) avoids too much rubber adhesive being applied to one spot. Using a steady, sway-like motion is the best method to apply both types of rubber sealant.

The cure time is similar at around 4 hours to have dried sufficiently. However, at least 24 hours will be required to cure completely.

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On wet surfaces or if there’s been precipitation with an exterior application, allow for 48 hours for curing due to the added moisture.

Overall, the cure time is not majorly different between Flex Seal and Leak Seal spray products.

Read Also: Dicor Lap Sealant Cure Time

Durability of Leak Seal vs Flex Seal?

The durability is consistent between these two rubber seal solutions.

Rust-Oleum Leak Seal – An effective seal can be applied and will last several years. It’s a good idea to recheck the seal every so often to ensure it hasn’t cracked through. Leak Seal is also highly resistant to temperature variations, which makes it effective on RV roofs and elsewhere that attract considerable heat or cold through the seasons.

Flex Seal – Strong seals can be achieved and will be strong for several years. The rubberized surface is somewhat flexible. It stretches as needed to maintain the seal. However, with extreme temperature changes such as in desert heat or Alaskan temperatures, Leak Seal probably has the edge on Flex Seal.

Closing Thoughts

The Rust Oleum Leak Seal flexible rubber sealant is a capable product. It does appear to manage temperate variations at the extreme end of things very well. With that said, Flex Seal is no slouch and is reliable.

In this article, we’ve mostly discussed the spray versions of both Leak Seal and Leak Seal. Yet, the liquid versions are just as capable, and both have their place.

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