Flex Seal: As Seen ON TV!
There is your answer.
Junk.
If it were good then real stores would sell it.
There is a product made for this:
SR Speciality Recreation. Holding Tank Patch. called INSTA
made to peel and stick as a patch.for ABS and polyethylene tanks. "long lasting"
Eternabond is great stuff. Im not sure about taping it to water tanks with the sticky side on the wet side. It likely will fail.
Use 2-part epoxy that is specific to plastics. Hardware stores or Walmark has it.
Sand and clean the area well.
Use fiberglass fabric in the mix if more strength is needed. Layer more on after a short drying interval per directions, or just when it dries to a tack. If dry overnight,then lightly sand then clean, then apply more.
