Not satisfied with the flow rate he was able to achieve with his Super Soaker, Gordon decided to upgrade to a backyard dunk tank. By hooking up an off-the-shelf sump pump to a power supply and building in microprocessor control, he can blast a victim with up to 5 gallons of water when the target is hit. Switch inputs control the "douse" time from one to nine seconds. The microprocessor clocks data into a shift register to control the seven-segment time display. For easy disassembly and transport (it's great for office parties!), the frame is constructed of 1.5-inch PVC tubing screwed together.

For PDF links to Gordon Wall's instructions and drawings:

Dunk tank information
Sump pump directions
Dunk tank B.O.M.
Schematic drawing of sump tank
Schematic drawing of modified outlet