At about 2300 eastern time, a Piper PA-28-180 lost power shortly after departing from Orange Country Airport and was damaged when it hit a drainage ditch on landing. The flight instructor and student pilot were not injured. The instructor said they had completed a 1-hour cross-country flight and were planning to practice takeoffs and landings. During the departure, the airplane climbed to 300 feet agl and lost power. Inspection revealed the fuel line between the fuel pump and the carburetor was loose at the connection point on the carburetor. Blue stains were observed on the outer skin of the airplane, from the firewall area aft about 4 feet aft. The airplane had accumulated about 20 hours of operation since a 100-hour inspection was performed on April 25.