guy at the hardware store said he used it in his troughs, I am about done with this trough, the seams blew out a while back. had a "discussion" with the other half (to be fair, he is the one doing the work on it) and he went with the hardware guy's recommendation. I was pushing for "as seen on tv" flex seal tape and/or paint. stuff has worked great on my old swimming pool.
Had a cracked toilet tank... 25 yrs old... can't find another one anywhere, didn't want to replace the entire toilet (holy cow, those suckers are way more expensive than I'd remembered!). Dried it out good, sprayed a couple of layers of FlexSeal on the entire inside of the tank... that was probably 5 years ago... still not leaking. knock on wood.