Method for Billing Certain Multi-Unit Properties

Historically, WSSC has billed multi-unit residential properties such as apartment buildings using a “unit count” method. This particular billing method provided consistency with the way single-family residential properties were billed. The unit count status allows us to divide total gallons by the number of units at a particular property. This lowers the Average Daily Consumption (ADC), which in turn, lowers the billing rate based on the ADC in gallons. 

Because there has been a trend towards building mixed-use multi-unit properties that contain a majority of residential units as well as one or more commercial units, we adopted Standard Procedure (SP CUS 11-01, effective December 31, 2011), which specifically addresses how WSSC will bill “mixed-use” multi-unit and “multi-unit residential” properties.

To receive unit count billing credit for the number of occupied residential units, please complete and return a mixed-use form via email to or via mail to WSSC’s Customer Service Department, 14501 Sweitzer Lane, 9th Floor, Laurel, MD 20707.

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