Fabian Espindola scored a brace for DC as they edged to a 2-1 win at Jamaica's Waterhouse, who remain top of Group Four.
But while Waterhouse have played all four of their group matches, DC still need to face Tauro twice.
It leaves Ben Olsen's men well-placed to reach the quarter-finals, thanks to Espindola.
Will Johnson's speculative 25-yard effort just before the half-hour mark saw the Timbers go ahead again as Olimpia goalkeeper Noel Valladares palmed the ball into his own net.
But Urruti's second goal and a Rauwshan McKenzie header after the break saw the Timbers to their win.
Caleb Porter's men jumped to six points, level with group leaders Olimpia but having played a game less.
Liga MX side Cruz Azul clinched their first win in Group Six, easing past Panama's Chorrillo 3-0.
