The Honolulu Board of Water Supply on Monday unanimously approved a 70 percent increase in water rates through the next five fiscal years.

The first in the series of five rate increases will likely add $6.99 a month for a typical Oahu residence.

The board’s decision means rates will rise 9.65 percent every year starting January 1, 2012, when charges will increase to $3.06 from $2.79 for every 1,000 gallons of water.

The current average bill of $39.19 will climb $27.53 to $66.72 with the last increase in July 2015, the beginning of the city’s 2016 fiscal year.

No one from the public testified on the rate plan Monday; a public hearing on the proposal was held in August.

When told of the increase Monday, Aiea resident Shannon Recaido was not pleased with the prospect of a higher water bill for her single-family home.

"It’s already so expensive to live in Hawaii," she said. "It all adds up. So I’m not too happy about it."

Kristi Stewart of Kaneohe said, "It’s never a good thing to have to pay more for water every month."

The board could decide to help low-income customers with their rates, but that would increase costs for other users, said acting board manager Dean Nakano.

Better conservation efforts, ironically, have increased the pressure to raise rates, Nakano said.

"As people save money it does reduce our revenue stream," Nakano said. "But it doesn’t take away from the fact that we need to sustain our operations and find the means in which to fund appropriately what it takes for operations and maintenance."

The agency maintains nearly 2,100 miles of pipeline, and 45 percent of the pipes are more than 40 years old, Nakano said. In addition, 317 miles of pipeline are nearly 100 years old, he said.

An estimated $203 million of the new revenue will go toward $345 million worth of projects to install, repair or renovate more than 250 water supply sites, including about 40 miles of pipeline, more than 210 wells or booster stations, more than 30 reservoirs and 10 water treatment facilities, among others.

But Nakano emphasized that higher rates and new pipes do not mean the end of broken mains that regularly disrupt traffic around Oahu.

"The water rate increase will not eliminate water main breaks that will occur," Nakano said. "It will help us replace those pipelines that are aging."

In a statement, board Chairman Randall Chung said a rate increase is necessary "to keep our water infrastructure and treatment systems operating properly to deliver a safe and dependable water supply. Deferring a water rate increase would only result in increasing costs and delaying necessary improvements."

Board member Denise DeCosta voted for the increase — with reservations — and expressed concern "whether we are biting off more than we can chew."

"With a large (rate) increase," she said, "there’s more pressure to get more projects out."

Nakano said in response that crews will "ramp up" projects gradually.

Correction:  The rate increase will start January 1, 2012. An earlier version of this story said it would start in mid-2012.