A winter average is established in January and February of each year. Water usage is averaged between the February and March billing periods. That number is used as your average household water usage for wastewater volume charges from the April bill until the following March bill, regardless of the amount of water used. Residential customers have a set charge for wastewater each month. That way, if you use water for your yard, to fill a pool, if you have a leak, or for whatever reason during the year, you’ll have to pay for the water, but won’t pay extra for the wastewater.