1. Obtain the PVC pipe and attatch the cap to one of the ends with liquid nails. Be sure to let the glue completely dry.
2. Prepare the dry ice by first breaking it into pecan sized chunks and powdering it in the blender. Be sure to use a blender that you do not care about. The dry ice is powdered because it will cause the cannon to discharce faster. (when handling the dry ice always use insulated gloves and safety goggles and wear clothes that completely cover your skin, it will burn any skin it touches)
3. store the Dry ice in a cooler.
4. Prepare the tennis ball by either wrapping it with a coffee filter or by wrapping it in a paper towelle
5. go to a secluded area, away from people or animals for the firing, do not fire while holding the cannon because it might explode.
6. Prop the cannon up on somthing that is not worth money because it might become damaged. 
7. fill the bottom of the 30 oz bottle with about a inch of dry ice powder and fill the rest with water. do not cap until ready to insert.
8. Screw cap on tight and slide into the PVC pipe, quickly insert the tennis ball and push it in with the stick. (safety goggles and insulated gloves and clothing should be worn at all times)
9. run to a preselected location behind the opening of the cannon at least 300 feet away. do not approach the cannon under any circumstance unless the ball has been launched.
10. Repeat as desired

DO NOT ATTEMPT IN AN AREA WHERE IT IS ILLEGAL YOU WILL GO TO JAIL!