Voters in parts of Fairfax and Prince William counties will go to the polls Tuesday to decide seven primary contests in this year's special House of Delegates election.

The polls will be open from 6 a.m. to 7 p.m.

For information on voting, call the following numbers: Fairfax County, 385-8100; Fairfax City, 385-7890; Prince William County, 369-9369. There are no primaries in Arlington or Loudoun counties or in Alexandria or Falls Church.

The five Republican and two Democratic primaries are being conducted in new House districts. The statewide redistricting, combined with an election one day after Labor Day and the traditionally low turnout in Virginia primaries, has led election officials to predict that fewer than one in 10 eligible voters will go to the polls.

The 1982 off-year elections are being held because the 100-member House, trying to redraw its boundaries to conform with population shifts revealed by the 1980 Census, could not come up with a map acceptable to the courts and the Justice Department in time for the 1981 vote. The courts allowed the 1981 elections to be held in temporary districts but ordered the legislature to draw another redistricting plan and required the 100 House members to run again this year.

The General Assembly finally devised a plan that subdivides the state for the first time into 100 single-member districts. Northern Virginia voters who now live in districts represented by two or three delegates will be represented by only one.

Primaries are scheduled in six Northern Virginia districts. Only the 37th District, which includes Fairfax City, has Democratic and Republican primaries. The general election Nov. 2, by contrast, will feature contests in almost every legislative district as well as congressional and U.S. Senate races.

The complicated redistricting will require 17 ballot combinations in November in Fairfax County alone, according to registrar Jane Vitray. Next year, when state senators and supervisors also stand for election, the county will have to prepare 40 separate ballots.

Virginia voters do not register by party and any voter living in a district with a contest may vote in Tuesday's primaries. In the 37th, voters will have to state a preference for a Democratic or Republican ballot. In the other districts, only one party ballot will be available.