Complex sentence: When Ned Flanders catches on fire, the fire department tries to extinguish him, but it does not work because Bart is pulling a prank with the fire hose, though the water crashing out of the gym with Bart does save Flanders anyway.
Split into simpler sentences: When Ned Flanders catches on fire, the fire department tries to extinguish him. It doesn't work because Bart is pulling a prank with the fire hose, though water crashing out of the gym saves Flanders anyway.