The Suffolk County Water Authority Wednesday night approved a 4.2 percent annual rate hike starting April 1, but several board members said the agency should continue working to devise a new rate structure promoting conservation among customers who are the heaviest water users.

The five-member board voted unanimously for the rate increase, which will bring in about $5 million in revenue and increase the bill for a typical homeowner who uses 160,000 gallons annually by about $15 a year — going from $365 to $380.

The authority board also raised wholesale water rates 5 percent even though consultants had recommended a 7 percent hike. Officials say the change was needed because several water districts that buy water from the authority are being subsidized by regular authority customers.

Patrick Halpin, one board member, asked the staff to make a priority of pursuing a multi-tier rate approach so that the authority’s heaviest users “pay the true cost of providing water,” though he acknowledged more study is needed “to get it right” and avoid unintended consequences.

James Gaughran, authority chairman, said more study is needed on how to structure the rate to avoid having an undue impact on places such as trailer parks and apartment complexes, which use less water on a per capita basis than a homeowner with a sprinkler system.

Authority officials say revenue is needed to deal with rising costs such as power and health insurance, as well as the need to replace the authority’s aging infrastructure, which includes 6,000 miles of water mains. The authority in the 2016 fiscal year is looking to increase its spending on pipe replacement by about $4 million, up from $10 million in the current fiscal year.

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