Admittedly, this might be working as intended. I built some algae terrariums in water to reduce the upkeep and quickly found my dupes frequently disinfecting. The germ overlay indicated why. I went back to before finishing the algae terrariums and I guess I forgot the water was tainted at some point. Went from under 700 germs in any given square of water to consistently more than a million.
Build algae terrariums and fully immerse in water with germs