Umanzi omhlophe uyisisekelo esibalulekileyo kumasebenzi, njengokwenza izinkomishi noma ukuchitha emazikhospitali. Ngamanye amazwi, amanzi asebhalini ayikwazi ukuthi yizinye izinto zokwenza lezi zinto. Lokhu kukhona izimboni ezithile ezibizwa ngokuthi izinhlangano ukubuyela emuva kwe-RO ukuhlanzwa kwamanzi izisitemu ziyakha. Zibhala njengamafiltara amakhulu okukhupha konke okubi kwamanzi, kwenza ukuthi kubhekhwe kakhulu. Ngokufanana nesifili esihle esikhipha izinto ezincinci okungakwazi ukubona. Lezi zisitemu zininkulu nezinhloso, zwenziwe ukuzisebenzisa amanzi angaphezu kwezinkulu emakhasini, akasenziwa kuphela ukusebenzisa kwehause. Bazithimela amanzi ngendlela eyodwa ephuma kuphela amanzi amhlophe, kusasa isithakatha. Kuyindlela enobuhle futhi emakhasini inamanzi amhlophe abonakala ukusebenzisa ngokuvunywa.