City of Santa Rosa > Departments > Finance > Revenue > Utility Billing > Wastewater (Sewer) Charges

Explanation of Wastewater (Sewer) Charges

Sewer charges for most single-family residential customers are determined by an account’s "sewer cap." To determine the sewer cap we average the water usage during the winter billing periods. This occurs during the months of November through March. We use these billing periods because these are normally wet months when it can be reasonably assumed that virtually all water is used indoors and exits as wastewater. The average monthly indoor water usage is called the "sewer cap." For example, let’s assume winter water usages were as follows:

Winter Billing Period 1:

7,000 gallons

Winter Billing Period 2:

5,000 gallons

Winter Billing Period 3:

6,000 gallons

Average winter water usage = 6,000 gallons

The annual sewer cap starting on the next July bill = "6"

In the above example, on the next July bill, the following sewer charges would appear:

Sewer fixed fee


Sewer usage fee

$76.74 (sewer cap of "6" x $12.79)




Size of Household Average Sewer Cap Range
1 person 1.5 - 3.5
2 persons 3.0 - 5.0
3 persons 4.0 - 6.0
4 persons 5.5 - 7.5
5 persons 6.5 - 8.5
6 persons 7.5 - 9.5
7 persons 8.0 - 10.0

For each person after seven, add one to each end of the range.

NOTES: 1) Sewer caps are re-evaluated annually, based on the prior winter’s water usage. The less water used, the lower the sewer cap; 2) If monthly water usage is ever less than the sewer cap, the sewer usage charge is based on water usage, not the sewer cap; 3) Customers who do not use their domestic water meters to irrigate outdoors may not receive a sewer cap and may be charged based on actual water usage; 4) For residential customers who use non-City water part or all of the time, the sewer cap is established on the average winter use of similar households with City-metered water.