I built two immersion chillers this weekend (50' x 1/2 and 50' x 3/8). Here are my thoughts.
I went to Home Depot on Friday and all they had was 1/2in OD copper. I got a 50' roll, some 1/2 ID Vinyl tube and a both a male and Female hose repair kit.
I got home and filled a Cornie with sanitizer (had a batch ready to transfer). Having the extra weight on the Cornie helped a lot when bending the copper into a tighter coil. Wraping the copper around the keg was easy enough, but bending the ends into a vertical position was a pain. After kinking the copper more than once and a few four letter words, I ended up with a 40' coil (I lost 10' due to bending the uprights).
Ok... Let's curve the uprights... Damnit, bent it again... Long story short, I could not put a tight enough radius on the copper to curve it enough to make it look like a racking cane. I got about 90 deg and quit. I slipped the hose on, clamped it down and tested it.
4 1/2 gal. from boil to 80 deg in ~ 10 min... thats pretty good... 80 deg to 76 deg another 15 min (Did I mention I live in FL!).
The wife and I were at another home depot on Sunday and I figured I would check for 3/8 OD... They had it, so I bit the bullet and got 50'.
I went home and ran through the same process, but this time with I wrapped the coil easily, made the bends for the uprights by hand without an issue, ans I used a can of spray paint to bend the hooks at the end. No kinks, go dents, no problems. done in ~25 min and still had all 50'. Yay!.
Ok, the only issue I had was getting 3/8 ID tubing over a 5/8 ID hose repair kit. I boiled some water, used some soap and a pair of pliers and it worked. The process: Heat the hose end and the brass repair fitting in the boiling water, pull out the tube and insert the pliers in the hose and stretch it, while stretched insert the hot fitting in the tube, use a rag or other heat resistant method to grab the tube and finish pulling it over the barb. (I placed the barb on the counter and pushed the hose over the fitting). This took several attempts, but in the end it worked.
I plan on using the ugly 1/2 OD chiller as a pre-chiller in an ice bath (so no one can see it) and feeding the 3/8 OD chiller in the wert. I have not had time to test this yet, but I will post back next time I brew ~ two weeks or so.
Word to the wise, ONLY USE 3/8 OD copper unless you have special tools and / or skills for 1/2 OD copper. It is MUCH, MUCH easier. You will thank yourself. I talked myself into thinking that 1/2in is so close to 3/8in that it can't be much harder (WRONG).
You have been warned.