Mike Ribeiro scored and Braden Hotlby stopped 35 shots for the Southeast Division-leading Capitals (24-18-2).
While Anderson was rarely tested, he did make some timely saves to bail out his team in the third. With the Senators holding a 2-1 lead midway through the final period, Anderson made a huge save on Eric Fehr when he skated in on net all alone.
Turris, who had an empty-net goal with 1:27 remaining to seal it, opened the scoring early in the second, beating Holtby for his 100th career point with a shot the Capitals goalie should have stopped off the rush.
The Capitals tied it midway through the period when Ribeiro, standing just outside the crease, hit the puck out of midair to beat Anderson.
But the Senators got the lead right back just over two minutes later when a bad pass from behind the net by Holtby landed right on the stick of Conacher, who easily made it 2-1 on the turnover.
The Senators have won eight of their past ten at home against the Capitals, including a 3-2 victory Jan. 29 in the first of three scheduled meetings between the teams this season. The series finale is in Washington on April 25.