@dushman we actually have had a "fatberg" clogging which required a plumber because a small cleaning spiral didn't work. guess it was the buildup of decades.
the problem is that those things can collapse, one day everything works fine, next you have an ultra-clogged pipe somewhere deep in the guts.
@dushman the problem is that there is no flow if the fat collapses, so it never gets there :)
@dushman if you do it regularly it might help i suppose, but this clogging was after more than 5 meters into the pipe. you'd have to put lots oh NaOH into it to have the right concentration at that distance.
after the plumber poked a hole we just let hot water run for a while and things were good. like i've written it was the buildup of decades.
i mostly use butter now and use it sparingly enough that there isn't much left to pour into the drain anyway. can't remember when i've deep fried something :)