Flex Seal is a rubberized waterproof sealant that works for a lot of different applications, but will Flex Seal work on a toilet? While we don’t recommend using Flex Seal spray for toilet repairs, we do suggest using Flex Caulk or Flex Glue. With Flex Caulk, you can create a watertight seal around the base of a toilet to help prevent leaks and give your porcelain throne a finished look. Flex Glue can help seal and bond cracks in the toilet bowl or tank. It’s important to note that Flex Seal products are not designed for high-pressure applications, so they wouldn’t be suitable for repairing the hose carrying water to the toilet. You may need to call a plumber for that one!