Fairfax County yesterday joined three other communities in offering its surplus water to the drought-stricken town of Round Hill, Va., which yesterday began a rationing program allowing its residents to turn on their taps for just six hours a day.

The town of 650, however, hadn't made up its mind that it needed the help, according to Mayor Jeffrey Wolford. "If we can handle it on the local level, I think that would be good," Wolford said yesterday.

The mayor said the town council will wait until Thursday before deciding whether to accept the 22,000 gallons a day that the Fairfax County Board of Supervisors voted yesterday to truck to Herndon Junction from the country's Occoquan Reservoir.

"We would like to have a few days to see how the water rationing affects the citizens of the town and to see what impact the snow and rain has on our reservoirs," Wolford said.

Round Hill, situated in Loudoun County, 47 miles west of Washington, received five inches of snow early Monday.

The town, which has had a continuing problem with water shortages, has two reservoirs - one with a capacity of 200,000 gallons, the other 10 million gallons. According to Wolford, both are now at record lows.

The rationing plan limits water use to two hours in the morning, two hours at lunchtime and two hours in the early evening. Wolford said the town hall received no complaints about the rationing program during its first day.

The town normally uses about 40,000 gallons of water a day, and, according to public works director Ralph McGehee, the water offered by Fairfax would be enough to supply the town's needs if residents used water sparingly.

Purcellville has offered the town 15,000 gallons of water a day and the town council has also received offers of help from nearby Jefferson County, W. Va., and from Shawnee, a community west of Winchester.