How long before they call a game because of rain?

The Nats are in Florida and the game has been in delay because of rain, 5 complete innings have been played and Washington is up 7-1! I believe 5 innings is enough to call the game a Nats win no? This is severely holding up my fantasy playoffs! Please let me know, I know the Yankees play the rain delay game in their favor but is there a time limit before the Ump says enoughs enough?