What is Sewer Averaging?

Sewer averaging is a calculation method used by some jurisdictions that average water consumption for sewer service charges on utility bills. The City of Ferndale recognizes that during the summer months, residential properties often use water for activities such as filling pools or gardening, where that water doesn’t contribute to the sewer system. To ensure accurate sewer charges, various methods of sewer averaging have been applied over time, with the City adjusting its approach in an attempt to establish a fair calculation that neither overcharges nor undercharges residents for sewer usage. The City only uses the sewer averaging for single family residential homes. 

In 2021, the City introduced a new sewer averaging method designed to promote consistency in utility billing, where sewer charges were the same for each billing cycle for the year, based on the previous year’s water usage. 

However, following feedback from residents, the City Council approved a return to the “traditional” method of sewer averaging, effective January 2025. This method, which was used prior to 2018, incorporates “winter months” to determine sewer charges in the summer billing periods, while reflecting actual water usage during the winter billing periods. As a result, residential customers will no longer see a fixed sewer charge for every billing cycle, but rather a charge that is more accurately aligned with recent consumption patterns. 

For the purpose of the above illustration, the “Winter Months” are highlighted in blue, while the “Summer Months” are highlighted in yellow. The billing periods for December, February, and April (blue) will reflect actual water consumption for both water and sewer charges (ex. 5 units- charged 5 units for water and 5 units for sewer). Conversely, the billing periods for June, August, and October will reflect actual water consumption for water charges, but the sewer charge will be based on the average water consumption during the winter months (October through March). 

Here is an example using the illustration above:

To view the current rate sheet effective 2025, please click here. If you have any questions about averaging or your utility bill in general, please contact our utility billing clerk at 360-384-4269 or utilitybilling@cityofferndale.org.