becuase if you want to purify the water you need to buy building components from the npc to build a structure using sieve plates and sedimentation tanks to purify the water
thats odd genuinely couldn't tell you what happened because I've tested the game a couple times now and it works fine for me, but its likely there is an oversight in my code. try quitting to menu and restarting the game and see if that helps .
Ok I managed to replicate the bug, it happens if you still have water bottles and try to get more from the purifier it sets the purity to 0 on your water and it never goes up from there. I assume you're averaging the quality of the water but once you go below 1 it just multiplies by 0 forever.
I see I tested it and it happens if the purifier has 0 bottles to give and you click e again. This causes the purity to 0 becuase if there is no water in the purifier the default value is 0. Really easy to fix I just need an if statement. But it is what it is