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.

For the billing of certain multi-unit properties, WSSC will apply a billing credit after the following steps have been completed:

  1. Submit a Unit Count Postcard Questionnaire: This document can be found under the Required Documents portion of this page. The questionnaire allows WSSC to gain more specified information on the number of high flow and non-high flow commercial and residential units at the mixed use property.
  1. Submit a Reconciliation Recap Form along with a current rent roll: The Recap Form should be filled out using the previous billing statements (available on your water account) as well as your own documentation. For more instructions on how to complete the form, please reference the Required Documents portion of this page.

All documents should be submitted via email to or by mail to WSSC’s Customer Service Department, 14501 Sweitzer Lane, 9th Floor, Laurel, MD 20707. WSSC will review the account information and apply a billing credit if applicable. For additional information, please contact our Customer Care Department at 301-206-4001.

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