New York City officials signed off on an 8.5% water bill hike for property owners on Thursday — the largest increase since 2011.

The city Water Board begrudgingly approved the new rates during a meeting where the group also passed a resolution saying they were forced to approve such a steep hike due to a budget maneuver by Mayor Eric Adams.

The members said Adams imposed new fees on the Water Board, an independent agency that oversees the city’s water supply. The resolution said the increase will make it more difficult to justify water bill hikes in the future, which could limit board's ability to fund infrastructure to handle increasing rainfall and rising sea levels caused by climate change.

“It undermines the board's ability to consider rates in the future for critical water infrastructure, like storm water resilience and coastal resilience,” board member Dan Zarrilli said in an interview after the vote.

The increase will add $93 to the average city property owner's water bill, from $1,088 to $1,181. The new rates go into effect July 1.

Adams in May ordered the Water Board to pay a new “rental charge” in order to help plug the city’s budget gap. The city built and owns the water infrastructure but technically “rents” it to the New York City Water Board.

The Water Board paid those rental fees starting in 1985, but former Mayor Bill de Blasio canceled those charges during his first term. Adams this year brought them back, which led to such a steep hike, Zarrilli said.

Opponents of the rental charge call it a “backdoor tax” that disproportionately impacts lower incomes, unlike the city’s normal progressive taxing systems such as income and property taxes.

The Water Board’s protest resolution noted it was obligated to pay Adams’ rental charge and that it expects the mayor to increase the same fee in the future. According to budget documents, Adams plans to bring in $1.4 billion from the Water Board over the next four years.

The mayor’s office did not respond to questions about the Water Board’s resolution or how the rental charge would impact future spending to combat climate change. The Adams administration has previously said charging the Water Board was necessary to prevent cuts to city services.

Councilmember James Gennaro, who represents eastern Queens, lashed out at Adams for the increase and praised the Water Board for taking a stand against what he called an “unjust practice.”

“This is a promising development in our fight to ensure New Yorkers are not subject to a backdoor tax,” he wrote in a statement, “which financially burdens all New Yorkers, but most especially low-income families.”

Only property owners pay directly for water, but landlords tend to build the extra cost into the rents they charge. Unlike other utilities like gas and electric, the mayor has direct influence over the cost of water through the rental charges to the Water Board.

According to a budget presentation by the Water Board’s last month, Adams’ new charge is responsible for about a third of this year’s increase. Another third will be used to pay for capital projects such as improvements to the Hillview Reservoir in Yonkers and water tunnels in Westchester County.

Eliminating the mayor’s ability to collect the rental charge would require state legislation. Gennaro has proposed city legislation he hopes would at least discourage mayors from charging the fee by requiring ratepayers be notified of the charge in advance.

“This is only just the beginning, and I will stop at nothing until this hidden tax is done away with,” Gennaro said.

Correction: A previous version of this story misspelled Dan Zarrilli's name.