Does Flex Seal Work On PVC Pipe? (Find Out Now!)

Dennis Howard
by Dennis Howard

You notice that you have a leak from a PVC pipe in your home. Immediately, your memory returns to a TV commercial for a flex seal product that claims to seal PVC pipe. A quick trip to the home improvement store, and you soon have a spray can of the flex seal product. Now the real test. Will the flex seal work on the PVC pipe?

Flex Seal is a family of sealing and bonding products produced by the Swift Response company from Weston, Florida. The aerosol Flex Seal product is a rubberized spray coating advertised as a sealant for most products. According to the Swift Response company, Flex Seal will bond with most materials except silicone.

In general, Flex Seal can be used on PVC pipe as a temporary repair for small leaks and cracks. However, the temporary nature of the seal provided by Flex Seal necessitates more permanent repairs in most situations. Flex Seal should not be used as a permanent fix for any leak in PVC pipe.

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What is Flex Seal?

Flex Seal is a rubber-based seal coating material. The company, Swift Response, states in their advertising

Flex Seal can be used on almost every surface: wood, metal, tile, concrete, masonry, fabric, glass, plastic, aluminum, porcelain, drywall, rubber, cement, and vinyl.

The rubberized sealant material sprays on a surface as a thick liquid. The thick liquid seeps into cracks. The rubberized sealant cures on contact with the air to form a rubberized surface that is waterproof. In theory, this seal becomes watertight and almost airtight once fully cured.

In advertising, the manufacturer claims that Flex Seal can stop leaks in piping, repair damaged pots and ceramic ware, and even waterproof a boat. To some extent, these claims are true, but underlying issues aren’t often described.

The Claims and the Actualities

The advertisements for Flex Seal are filled with examples of how Flex Seal is used. These advertisements include a boat with a screen window inserted in the bottom. The screen is treated with Flex Seal, and the boat is shown floating with a man in the boat and no leaks. Other examples show pipes with various size holes being repaired with flex seal, including pipes under pressure.

Many news reporters and testing laboratories have conducted similar experiments with surprising results.

The Boat Test

Consumer Reports, a leading consumer product testing company, replicated several Flex Seal advertisements. One such experiment was the boat with a screen in the bottom. Consumer reports built a scale model boat and installed a screen bottom in the boat. The screen was treated with Flex Seal. Consumer Reports found that the scale model boat did, in fact, float.

However, the boat was a small-scale model. It was not large enough to test with a human occupant. Other replications by Consumer Reports were not as successful. The most striking example was the leaky pipe test.

Leaky Pipes

Consumer Reports drilled various size holes in a copper pipe and then treated the pipe with Flex Seal. Multiple coats of Flex Seal were required to fill the larger holes in the copper pipe. When pressurized water was introduced, the larger holes blew the sealant off the pipe.

The Flex Seal did manage to stop leaks in the smallest of holes but was entirely inadequate at stopping the pressurized water. Obviously, Flex Seal will not create a stable leak repair on cracks or holes of more than pin size.

Cracks and Openings

Several investigative reporters used Flex Seal to stop leaks in cracked pipes, gutter seams and even on cracked terra cotta planters. These tests met with varying results, mostly on the negative side.

Sealing cracks on PVC pipe seemed to have the best results. Small cracks don’t put the Flex Seal to the same stresses as larger and wider openings. Cuts or breaks in the PVC pipe typically didn’t hold well during the tests.

Separated gutter seams didn’t fare much better. The liquid spray-on rubber sealant simply ran through the seam and failed to form any kind of barrier to leaks. If the gap is more than a few millimeters wide, the spray coating can’t fill the opening before it leaks through.

So, How Do I Stop a Leak in PVC Pipe?

Flex Seal may temporarily stop a leak in PVC pipe and give you time to affect a more permanent repair. You should never consider a Flex Seal repair anything but a stopgap measure.

In general, the only way to permanently repair a PVC pipe is to cut away the leaking or cracked section and replace it with a new piece of pipe. Repairing PVC pipe is not complicated and doesn’t require specialized tools. Almost any homeowner can repair a broken or cracked PVC pipe. To repair cracked or broken PVC pipes, follow these steps.

Step 1: What You Will Need

Before starting your repair, gather the materials you will need to replace the leaking section of the PVC pipe. This may include:

  • Enough PVC pipe and the correct fittings to replicate the existing PVC pipe run
  • A pair of PVC pipe cutters
  • PVC primer and solvent cement
  • A tape measure and marker
  • Eye protection

Step 2: Cut Away the Damaged Section of PVC Pipe

Use the PVC pipe cutters to remove the damaged section of the pipe and any fittings. Keep the damaged section of the pipe as a reference.

Step 3: Construct a Replacement Section of PVC Pipe

Using the old section of PVC pipe, construct a replacement section. Try to make the replacement as close to the original as possible. You will place the new section into the plumbing using couplers on the ends. Dry fit everything before you apply and primer or solvent cement.

Step 4: Glue the Parts Together

Apply PVC primer to the pipe and fittings. Let the primer dry before applying the solvent cement. Then, apply solvent cement to each piece as you connect them. Don’t cement all the parts, and then put them together.

Step 5: Allow the Solvent Cement Joints to Cure Properly

Give the cement time to cure and harden properly. You should wait at least thirty minutes before applying any pressure to the pipes. When you repressurize the pipe, check carefully for any leaks.

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Is Flex Seal a Viable Option for Leaks in PVC Pipe?

If the leak in your PVC pipe is more than a few drips, Flex Seal is probably not the solution to your problem. Leaks larger than pinhole size will likely continue to leak even after the Flex Seal is applied. Flex Seal may be useful in an emergency, but always follow up with a permanent repair to a leaking PVC pipe.

Dennis Howard
Dennis Howard

Dennis is a retired firefighter with an extensive background in construction, home improvement, and remodeling. He worked in the trades part-time while serving as an active firefighter. On his retirement, he started a remodeling and home repair business, which he ran for several years.

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