Brainbashers!!

Came across this site (Brainbashers) - from my Gmail RSS feed.
Try this one from their Daily Puzzle -
Using a tap, a three gallon container and a five gallon container, can you measure exactly 4 gallons, you may empty the containers down the drain???

For answers - go to their website! :)
http://www.brainbashers.com/showpuzzles.asp?puzzle=ZNJY.

My answer was different from the websites, but it was a step longer :(.

Elf.