As an example, our water bill last month was for 10,090 gallons of water which cost $30.59 or about 1/3 cent per gallon. If we have an older toilet of, say 3.5 gallons, then each flush is costing me about a penny a flush. Not too bad. But considering the minimum charge for just being connected is $9.33 (for 0 gallons) the cost may actually be less. On the sewer side, we paid $44.96 or about .4 cents per gallon. The total cost is about 3/4 cents per gallon, which means each toilet flush is sending three pennies down the drain. There is, of course, a minimum sewer fee of 7.83 even if you use zero gallons, so that affects the calculation somewhat.
If you figure you use the toilet five times a day, for two people, you are talking 37 cents a day just for flushing toilets or about $136 a year (didn't see that coming). But of course, the big-ticket items are the washing machine, watering, car washing, and showering, which make up the bulk of our water usage.
This site provides some round numbers on water usage for various tasks and appliances:
|5-minute shower||10 gallons|
|5-minute power shower||20 gallons|
|Brushing teeth with tap running||2 gallons/min|
|Brushing teeth with tap off||.25 gallon|
|One toilet flush||3 gallons|
|Other water use (drinking, cooking, etc.)||7 gallons|
|Washing machine||40 gallons|
|Washing car with bucket||3 gallons|
As I noted above, there is also a minimum monthly charge for water in sewer, at least in our district. I found this out when I shut the water off when we went away. The meter reading for that month was zero, but we still got a bill for about $50 - half of which was garbage pickup (which you pay for even if you have no garbage) and half for the baseline fee for being connected to water and sewer. So even if you don't use any water at all, you have to pay. And in most jurisdictions, you have to have the water and electric hooked up in order to occupy a dwelling.