There should be a seam at the top of the tower or a cap that can be slid of the tower. Often these are stuck and may need a little enforcing to remove. Try to use a tool that will not scar the surface. Or, drape a hot wet towel over the cap first to hopefully free it.
Your pressure is fine if you are at sea level. Try increasing the line to six feet and if necessary, trim back four inches at a time until desired flow rate is obtained.
Scott Zuhse, Instructor
Micro Matic Dispense Institute