The sewer billing method for Coppell residents is switching to winter averaging.

Coppell City Council approved an amendment to the water and sewer regulations ordinance in September. The city began collecting data Nov. 1 to calculate each customer’s winter average. Residential customers will see these updates in their water bills beginning April 1, according to the city’s website.

Winter averaging is a method used to bill residential accounts for sewer service that uses winter months as the basis to calculate a customer’s sewer portion of the utility bill for an entire billing year. It applies to residential customers in Coppell only, according to the city. New customers will be assigned the citywide volume average until their winter average is established.

Sewer services were billed on a fixed cost prior to the switch. The fixed method capped billed usage at 13,000 gallons. Sewer service billing sharply increased during summer months, because sewer flow was not metered. Winter averaging will help remove the water used for outdoor activities from a customer’s bill.

The city will track water usage from November to March to calculate the winter average, according to officials. The highest and lowest months of usage will be removed. The city will then calculate the average water usage of the remaining three months and use it to determine the monthly amount residential customers will be charged for sewer services. The established volume will become the sewer volume that will be applied each month until a new volume is determined the following year.

The city estimates 73% of customers will see either no change or a decrease in their sewer charges.