Water and sewer rates in Montgomery and Prince George’s counties could increase by as much as 9.5 percent in the next fiscal year, according to documents that are part of early budget discussions.

Officials for the Washington Suburban Sanitary Commission have told the county councils for both counties that the utility would need a maximum 9.5 percent increase to pay off debt, rehabilitate and replace aging pipes, and cover fixed costs, such as electricity for its plants.

WSSC’s revenues haven’t kept pace with increases in operating costs related to population growth because of water conservation efforts, WSSC officials say.

Staff for the Montgomery council have recommended an 8 percent increase to account for continued “economic uncertainty” that WSSC customers face, along with mounting expenses for gas, electricity and health insurance, according to a staff report.

A 9.5 percent increase would add $6.65 monthly to the average quarterly WSSC residential bill, while an 8 percent increase would add an average $5.57 monthly.

WSSC spokesman I.J. Hudson said the county councils will decide spending limits to give direction to WSSC officials as they come up with next year’s budget, along with any rate increase proposal to help fund it. The 9.5 percent increase is a “projected” rate increase, Hudson said, but has not been formally proposed.

WSSC releases a draft budget by Jan. 15, with public hearings to follow. The utility must submit a budget to be approved by both councils by March 1. The new fiscal year begins July 1.

After no rate increases between fiscal 1999 and fiscal 2004, WSSC customers have faced nine years of rate hikes, ranging between 2.5 percent and 9 percent. Customers are paying a 7.5 percent increase during this fiscal year.