Sure, water can get polluted by substances added to it but it doesn’t disappear. Dirty water is H2O with floaters riding along. It can be cleaned by straining out the floaters.
I had an extended family member in Denver who was practicing, “If it’s yellow, let it mellow. If it’s brown, flush it down.” She would leave urine in a toilet because she didn’t want to “waste” water. I explained that when she flushed the toilet, that water didn’t just disappear. It goes through the sewer system and ended up at a water treatment plant where the floaters are strained out and the clean water is put back into the South Platte River. Some of it will then evaporate and fall as rain somewhere else. The waste solids are taken to a farm owned by the Denver Metro Wastewater Reclamation District and spread on the fields and crops. I use to lease the hunting on that 54,000 acre farm/ranch. It had not been legally hunted for many years and we took a lot of great deer and pronghorn there.
It is also true that with a septic field used by homes in the country that once the dirty water passes through and is filtered by the soil, it is clean again. I was told this by the engineer who designed my septic system. Some soil types strain out the floaters faster and some slower. The water leached into the soil at my place is clean after just three feet of soil. The point is that water isn’t wasted in the sense that it disappears forever. Our atmosphere is sealed. The water you drink came from somewhere else and was recycled by man or nature.