RSL improved to 13-10-4 and moved just four points behind the San Jose Earthquakes for first place in the Western Conference.
RSL entered the game with a 0-3-0 record in league games this month. It also had lost four consecutive road games dating to a 3-0 victory June 16 at Chivas USA.
But RSL improved to 2-0-3 all-time against the Union. All three draws have been on the road.
The Union's winless streak reached four and this was their second straight draw. Philadelphia hasn't won since a 2-1 victory July 29 over the New England Revolution.
Philadelphia played without starting defender Sheanon Williams, who was sitting out due to yellow card accumulation.
The Union fell to 7-12-4 and remained in eighth place in the Eastern Conference.