Opposition to a proposed water rate hike continued to grow Friday even as Tennessee-American Water Co. sought to defray concerns by pointing out that some of the increase in water bills is because of hikes in the city’s sewer charges.

The Chattanooga Urban League and Chattanooga Chapter of the NAACP announced their support Friday for Fight the Hike, a coalition of business and government groups opposed to a rate increase sought by Tennessee-American.

Warren Logan, president of the Chattanooga Urban League, said the water company’s request for a 20.58 percent is “excessive” and will cause a hardship for many low-income Chattanoogans.

“These water companies are draining us dry in order to line the golden pockets of their shareholders,” Mr. Logan told reporters at a news conference.

Valoria Armstrong, president of the Chattanooga-Hamilton County branch of the NAACP, said the latest rate increase “is unjust,” coming after a 12.3 percent water rate increase in May 2007.

“Continually increasing rates for water and other utilities is going to cause a real hardship for many families,” she said.

Tennessee-American said its rate increases are necessary to cover soaring expenses for higher-priced chemicals, fuel and power needed to treat and pump water to its 76,000 customers.

In a full-page advertisement Friday in the Chattanooga Times Free Press, Tennessee-American also noted that the sewer portion of Chattanooga water bills has increased four times in the past 22 months while Tennessee-American had only one increase in the same period. In the past year, city sewer rates rose 6.2 percent, or about half as much as the increase in water rates by Tennessee-American.

In its bill, the water company includes additional charges to cover city-mandated sewer fees.

Water utility officials noted that its rates must be reviewed and approved by the Tennessee Regulatory Authority, while the Chattanooga City Council may set city sewer rates on its own.

“Our aim is to clear up confusion with customers regarding the relationship between the sewer and water portions of their monthly bill,” Tennessee-American General Manager John Watson said about the advertisement.

He also noted that, since July 1, only four comments have been filed about the utility’s rate increase with the Tennessee Regulatory Authority in Nashville, even though the Fight the Hike campaign has gained the support of the Chattanooga City Council, the Hamilton County Commission, the Chattanooga Association of Realtors and the two local civil rights groups.

“I would have hoped the Realtors, Urban League and NAACP would have gotten both sides before joining the city’s orchestrated attack against our company,” Mr. Watson said.