Does Flex Seal 'As Seen on TV' Really Work?

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I like watching the CrazyRussianHacker (CRH) because he cracks me up and he tests things, even things that seem completely useless to start with, such a "banana gadgets."

But then he tests things which are supposed to be extraordinarily useful, like Flex Seal. Does this stuff really seal as well as the commercials suggest? CRH duplicates some of the things the guy in the commercial claims are possible. And, you know what, he's not so crazy. He wore a respirator face-mask. I need to do that more often when I'm working with stuff like spray paint around the house.

What He Tests

He pokes two knife holes in a perfectly good 5-gallon bucket and sprays the holes with Flex Seal. He attempts the waterproof strainer trick, spraying a metal-mesh strainer (colander) with the rubberized sealant. And, he attempts to fix ceramic plant pot that had cracked apart during the cold winter, much like what is demonstrated on the commercials. He also decides to try it on a nail-hole in the sole of his boot. He was able to put two layers on everything, including really thick looking layers on the strainer, with just one can. He has so much left over at the end he decides to just go ahead and paint the entire plant pot black to use up the rest of the can. A 10-ounce can is supposed to cover 8 square feet, while a jumbo 14-ounce can covers up to 12 feet.

He waited for the first layer to dry a bit before spraying on the next. According to the Flex Seal instructions, you are supposed to apply several even cracks until you've filled all the cracks and holes. However, in their FAQ, they also recommend that you wait for one coat to completely dry before applying another. On the instructions, they say to apply several coats and then wait 24 to 48 hours before applying another coat. This other coat, I would surmise, is as needed. It cures fully in 48 hours.

I suspect that he could have saved what was left in the can by using the same technique as you would for spray paint. Turn the can upside down and spray until it sprays clean. This cleans out the nozzle so that sealant (or paint) does not dry and clog it up. I do not know if this really works for Flex Seal but since you are supposed to allow at least 24 hours before re-applying, you can probably keep using the same can. If you're like me, you've encountered sealants that become useless if you do not use the entire container at once.

One thing he discovers immediately is that you should not spray too much at once, but rather go for thin layers. Otherwise, much like spray paint, the sealant will drip and run.

CRH only waits about an hour before testing for water-tightness. I guess he doesn't like reading instructions, because, after all, he's crazy. He does point out that you may want to let it dry a little longer.

Results of Flex Seal Testing

CRH's boot didn't work out. Not because the Flex Seal didn't work, but because he discovered a much worse whole in the side of the boot, in an area on which the seal probably would not have worked. The bucket held water and the strainer became a water-proof container. As far as the ceramic plant pot, well it has a hole in the bottom which is supposed to be there, and the purpose was to basically bind the pot back together, not make it waterproof. This appears to have been successful.

Other Colors Besides Black

For when you want things to not be black, Flex Seal comes in other colors

  • White,
  • Brite (a bright white color)
  • Gray
  • Red
  • Yellow,
  • Terra-Cotta
  • Blue
  • Green
  • Almond
  • Brown

What Flex Seal Is For

According to these tests, even when not fully cured (I'm assuming) Flex Seal works. But let's be clear about what it is meant for. This sealant is meant to seal things against water. It is not for gasoline tanks or for containing any other liquid chemical. And, it is absolutely not to be used on anything that comes into contact with drinking water. This means you should not be sealing up your plumbing pipes with it, although you could use it on a PVC waste pipe, It should also be used in well-ventilated areas, which means mostly outdoors. You can use it indoors, but you should make sure that windows are open and there is plenty of ventilation. And wear a mask like CRH does.

Flex Seal is recommended for roof leaks, gutters, sealing skylights, leaky hoses, windowsills, PVC pipes, flashing, duct work, foundations, awnings, vent pipes, chimneys, downspouts, a/c drip pans, RV's and campers, trailers, and more.

The sealant will not withstand a lot of heat and pressure. For example, it's not a quick fix for leaky steam pipes, although those do exist.

As to the effect this stuff may have on the environment, well I cannot speak to that, but I would not assume it to be environmentally friendly. On the other hand, if you plan on using gallons of the stuff, you may need to consider calling a contractor!

CRH also tested Flex Tape and Flex Glue.

Another product that I really like to quickly seal up leaky things is Rescue Tape. The great thing about Rescue Tape is that it is not really sticky. You can remove it later without leaving behind a goopy mess.

Posted on 03 Apr 2018 01:41

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