In our scaled-down version of the Flex Seal promo, our skipper stayed dry (above right).
The claim. Flex Seal “stops leaks fast and is the easy way to coat, seal and protect almost anything,” the manufacturer says. In a promo video, pitchman Phil Swift applies Flex Seal to a screen door inserted in the bottom of a rowboat, then launches the boat with himself as skipper (left side of the photo above). It floats, of course. A 14-ounce can of the liquid is supposed to treat 2 to 12 square feet.
The check. Imitating the video for Flex Seal, we made our own tiny rowboat with a screen bottom, sealed the screen, and launched the boat in our lab “pond.” We also used Flex Seal on a copper pipe with drilled holes of different sizes, on an unsealed gutter, and on a cracked flowerpot. And we checked claims that the product is flexible and can be painted.
Bottom line. All aboard. Flex Seal floated our boat, and Teddy stayed dry. But with other uses, we hit rough seas. It took three coats of Flex Seal to plug the pipe holes, and larger holes blew out under water pressure. Even three coats didn’t seal vertical sections of our gutter’s end caps and joints: The product dripped down. Flex Seal was flexible but tore when bent too far. And although it sealed the crack in our flowerpot, we had to use two coats of spray paint to conceal our handiwork.
A version of this article appeared in the June 2012 issue of Consumer Reports magazine with the headline "Flex Seal: Handyman in a Can?"