How is the (residential) sewer bill calculated?
Due to the fact that it is not cost-efficient to meter wastewater use, the City of Irving uses an averaging technique to bill for wastewater services. We average your water consumption in winter months (January, February, and March as reflected in the bills received by customers for the months of February, March, and April) and then apply that average to the wastewater rates.

This is considered to be the best time to measure wastewater, as most customers irrigate less in these months, thus most water consumption is sent to the wastewater collection system after use. For example, if the water usage for January, February, and March is, respectively:
• 8,000 gallons
• 11,000 gallons
• 11,000 gallons
• Total: 30,000 gallons / 3 months = 10,000 gallons

In this case, the wastewater billed for the next year from May through April would be based on 10,000 gallons per month.

If a customer has not had sufficient time in the residence to establish a winter month's average, that customer’s sewer charge will be 80 percent of their water consumption until such an average is established.