On residential water bills the wastewater fees are a separate line item. In Santa Cruz there is a fixed fee for water delivery based on the size of the pipe (fee is independent of how much water you consume), a tiered fee based on consumption, and another fee for wastewater that is fixed tied to the household.
The fixed fees are very high. If I halved my water consumption then it would only save a dollar or so a month. The net effect is that the people who consume the least pay the most for the water they consume because of the high fixed fees. Here is my municipal bill for June last year:
17.41 Water - Ready to Serve 5/8"
4.71 Water Consumption Charges (3 CCF): 3 CCF @ 1.57
42.30 Sewer - Single Family
26.05 Refuse - 32 Gallon Cart
7.69 Utility Tax @8.5%
5.06 Franchise Tax - Water 3%,Sewer 3%,Refuse 12%
The water consumption does have tiered pricing, with a penalty above 10 CCF/month. As you can clearly see there isn't any incentive to save. I was also renting at the time, and couldn't do things like install more water efficient plumbing, fixtures and appliances (standard limits in rental agreements).