In a recent Mars flight series (on Netflix if i remember correctly) the water filtration machine broke midflight and the crew started to take it apart and stopped doing it - recognizing impossibility of such a repair endeavor - after taking out 4000 something pieces, and that failure put them into a mortal danger. (Sidenote: I had though to suspend disbelief as it looked completely unreal to me that one of the crewmembers - a USSR/Russian cosmonaut - wouldn't immediately rig a simple distillation device to make drinking water - everybody in USSR was doing it everywhere to make moonshine, especially in the "dry" places like ocean ships, remote military bases, etc., and i can do it myself in a few minutes with as little as 4 pieces of generic kitchen wares :)