i know what you are talking about. 10' of copper not going to give you alot of heat transfer. maybe it can but you going have to slow way down your flow rate or reserculate cooling water that is chilled by ice.
its up to you, how mach you are willing to spend? longer copper coil will give you a better heat transfer at faster flow rates and higher tap water temp.
i have a regular counterflow chiller that had a 25', 1/2"ID of copper tubing in a 1.7/8 cold water jacket. in one pass using a regular tap water i can chill wort to a yeast pitching temps with no problems.
