Washington Suburban Sanitary Commission customers will see their rates by 7.5 percent on July 1.
The rate will increase for residents in Prince George's and Montgomery counties and will add about $5 per month to the typical customer bill.
The increase will help pay for a two percent pay raise and some merit increases for the agency's 1,500 employees. WSSC officials say funds are also needed to rehabilitate and improve the agency's aging pipes and other systems.
The increases were approved in a meeting of the two counties' councils in Laurel on Thursday. It follows several years of similar rate hikes.
WSSC serves about 1.8 million residents in Montgomery and Prince George's counties.