BY SPEAR.  SPEAR I TELLS YA.. SPEAR

          THE GRAVITRON 2000 (TM)

                    These are plastic btw, they can be glass which is bad :)
                         _________
                        |         |
             |~~~~~~~~~~|         |
             |      OUT |         |
             |          | 5 US GAL|
             |          |         |
             |           \__   __/
             |              |_|
             |              | |__.   ___ valve.
             |              |_|  '
             |            __| |__
             |           /       \  /\ _Mouth piece and bowl (you need to make
          water level__ |_________|//   a bowl you can pop out quickly and the
             |          |         |/    mouth piece needs to be flexible like a
             \          | 5 US GAL|     piece of garden hose)
              \____  IN |         |
              |____|____|_________|
             PUMP       (hole near bottom)

                    You need to bore a hole in the side for the intake hose and
                    bore a hole in the top one for the output hose of the pump


   You fill the bowl with weed and place it in the mouth piece, turning on the
   pump will displace all the water from the bottom into the top creating a
   suction at the mouth piece. light the bowl when the pump is moving the water
   and the bottom will fill with smoke. Since you have a valve the water wont
   just fall back into the bottom jug. remove the bowl and put your mouth up
   to the piece, turn the valve and all 5 gallons of water will drop at once
   displacing all 5 gallons of smoke at once into your lungs.