MARIETTA — The new year will mean higher rates for Cobb Water System customers.

The county will implement an average 6 percent increase for water, and 2 percent jump for all wastewater customers on Jan. 1. County commissioners approved the price increases on Sept. 13.

For water, prices will not change for the first 3,000 gallons of water used. Customers will continue paying $2.83 per 1,000 gallons, up to 3,000 gallons.

But after that, the price per 1,000 gallons will increase from $4.11 to $4.36. That price covers usage up to 15,000 gallons.

Kathy Nguyen, the water system’s senior project manager, said a typical customer uses an average of 5,000 gallons per month. Those customers would see a 50 cent per month increase on the water portion of their bill.

Beyond 15,000 gallons, the price increases are steeper.

For usage between 15,000 and 29,000 gallons per month, rates will jump to $5.43 from $5.12 per 1,000 gallons. Usage of between 29,000 and 49,000 gallons per month will cost $6.36 per 1,000 gallons, up from $6. Every 1,000 gallons beyond that will cost $8.25, up from $7.78.

For wastewater, the rate will increase by 11 cents per 1,000 gallons used, from $5.30 to $5.41.

Despite the increase, Steve McCullers, director of Cobb Water, said the county will still have the lowest water rates in the region.

“We get calls every year about our rates,” he said. “Times are tough on everybody. People have problems paying not just water, but cable and electric bills.”

The higher rates are partly the result of infrastructure and other upgrades by the Water System, as well as pass-along increases from the Cobb-Marietta Water Authority, the wholesaler that provides water to the county and other retailers.

Those projects include water and sewer infrastructure projects; increased costs for chemicals and sludge handling; and large capital projects like the South Cobb Tunnel, a $305 million wastewater transport line that takes sewage 5.5 miles from Maxham Road at Old Alabama Road to Six Flags Parkway and Lee Industrial Boulevard in Austell.

Glenn Page, general manager of the Cobb-Marietta Water Authority, said his entity must also update its Wyckoff Water Treatment Plant in Acworth at a cost of $100 million to meet Environmental Protection Agency requirements on its disinfection byproduct rule.

The new standards deal with organic contaminants like leaves and grass that mix with water being pulled from Lake Allatoona, Page said. The EPA says the organic contaminants can form cancer-causing carcinogens when mixed with chlorine. Page said the improvements at the plant will remove any leaves and other organic contaminants before the water is mixed with chlorine, eliminating that hazard.

“We have federal mandates, but no funds,” Page said.

The water authority also has between $2 million and $3 million of work remaining at its Hickory Log Creek Reservoir on the Etowah River in Canton, Page said.

“Five years ago we were still underpriced,” he said. “But we had not anticipated the enormity of the renewal that we needed to do.”

City of Marietta residents, who get their water from the city-owned Marietta Power and Water, are also expected to see rate increases on Jan. 1, though city council has not yet approved the increases.