CFC question: size of outer hose x efficiency

ok, i'm making my own counterflow chiller, folowing this design: https://www.homebrewtalk.com/wiki/index.php/How_to_make_a_Counter_Flow_Chiller

everything is set, except for the rubber hose... i'm having trouble finding a 5/8'' one. I found a 1/2'', though, and although it's smaller in diameter than the one in the design, it appears to still leave enough room for the water to run through over the copper tubing. So, my question is: can I use this one or should I keep looking? Is there a relation between the inner diameter of the rubber hose and cooling efficiency? And in this case, if I bought a giant-sized (let's say, 1''), would it chill the wort faster?

It's all about the amount of thermal mass you have surrounding the inner tube. The more cold water you have surrounding the tube with wort the longer the water can stay cool. 5/8" would be better than 1/2" and 1" will be even better. I personally would keep looking for a 5/8" hose because 1" is a big over kill.

Try to find a "High Temp" garden hose. They can be found at home depot.

http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053