The dunk tank is the classic fundraising item. Throw 3 balls and dunk your boss or principle. The money earned from the balls goes right to your cause. Add a bunch of ice and watch the line grow long. Can be set up in 30 mins. You need to have a water source- we do not provide water. It takes 250 gallons of water to fill up the tank. Rock Rental charges 5% for credit card payments, no additional charge if paid by cash or check. Rock Rental's delivery fee is based on $2.00 per mile round trip without a trailer and the travel fee for 1 vehicle towing a trailer is $2.50 per mile one round trip from El Cajon with a zip code of 92021.