The Case of Flex-Seal FlexPaste and the Mystery Leak

According to the infomercials, Flex-Seal products can solve any leaking problem. Hype or fact? I put one to the test and found out.

The two of the many Flex-Seal products I've used successfully.
Two of the many Flex-Seal products I've used successfully.

Hype or fact?

Screenshot of the As Seen on TV home page.
Screenshot of the As Seen on TV home page.

As seen on TV!

Anyone out there not seen this advertising slogan, inferring the product has got to be great because it's advertised on television? Well, it's still a real thing. Just search for "as seen on tv" in your browser of choice, and you'll discover the phenomenon is alive and well. The slogan even has its own website for hours of perusing, boasting over 2600 unique and useful products. And, as you'd expect, there's even an As Seen on TV app, perfect for the busy person on the go who wants to keep tabs on this genre of products.

So, does the Flex-Seal range of products, As Seen on TV, live up to the hype? Read on, and let's see.

Leaky plumbing problem

Picture showing the wet carpet at the transition to tile; an odd spot for a leak.
An odd place for a leak!

Recently we discovered a wet area in our basement carpet. Immediately, thoughts went to one of our furry friends. The sniff test quickly put that suspicion to rest; it was plain water. But from where? It was in a very odd spot for a leak. Ah, what's behind the mystery panel?

I'd always wondered what might lurk behind the mystery panel, but not to the point I felt like checking. Now was my change! Removing the retaining screw, I discovered the source of the leak; it was emanating from the kitchen plumbing stack in the two spots shown below.

Picture showing the kitchen plumbing stack and two leak points.
The source of the leaks.

Plumber's putty to the rescue(?)

I had two products in my DIY arsenal, Oatey Plumber's Putty and J-B Weld WaterWeld. I also had a can of Flex-Seal spray but realized it wouldn't work for me in this situation, given the need to work behind the stack and in a wet environment (there was a lot more water by this time than shown in the photo).

Here's an important consideration when working with plumbing, always plan for future repairs and removal. For example, I could slap on the J-B WaterWeld, but that would create a permanent bond that is difficult to remove if needed. I wanted to keep the cleanout plug free to move.

So, I opted for the plumber's putty. Oatey didn't design their plumber's putty to fix leaks; they intend it to stop them in the first place by creating a seal. However, it stays flexible for decades, making it a great option for future removal. And it was handy. You can see it installed below.

Picture of the container of Oatey Plumber's Putty  I used in my project.
Oatey's Plumber's Putty.
A picture showing the plumber's putty around the upper leak.
Plumber's putty on the upper leak.

It didn't work, which wasn't all that surprising. But not wanting it to go to waste, I removed it and used it to seal along the wooden floor plate, creating a tiny coffer dam.

Flex-Seal FlexPaste to the rescue

At this point, I decided to research Flex-Seal to see what they might have to offer. My experience with their sprays has been excellent, so I hoped they'd have something for my need. And they did not disappoint; Flex-Seal FlexPaste looked to be just the ticket. A quick perusal using my Home Depot app showed it in stock at my nearby store. A quick addition to my cart, enter the appropriate payment info, and off I went to collect it. Easy Peasy.

FlexPaste is an interesting product, to say the least. It's the consistency of a thick meringue and just as sticky. The application went okay, but because it was so sticky, it liked my putty knife better than the cast iron plumbing. As a result, I ended up applying it by hand and moving it into position. While I often work with glues and epoxies bare-handed, I opted for latex gloves in this situation and am glad I did! It liked latex just about as well as the putty knife, but wetting my gloves in the water around the pipe defeated the attraction.

For the leak at the base where the pipe went into the concrete, I opted to use the J-B Weld because I could install it without restricting the cleanout plug. I worked this barehanded, and when it started sticking to my fingers, I wet them again and finished the job without further ado.

A picture of the retail package of the J-B Weld WaterWeld epoxy I used.
The J-B Weld WaterWeld epoxy I used.

Ta-da! The leak appears sealed. My handiwork won't win any beauty contest (as you see below), but it doesn't really matter in this case.

A picture of the FlexPaste and WaterWeld in place and currently stopping the leak.
Leaks stopped - for now!

The verdict...

So, do Flex-Seal products work as advertised? In my experience, yes, they do. They are excellent products for containing leaks. Would I assemble a boat with the product and head out on the lake to my favorite fishing hole? Even if it worked As Seen on TV, I'll give that a pass. Otherwise, I plan to keep on using Flex-Seal products for more pedestrian DIY projects.