Paul -
I found the email I sent to BD when I built my chiller. Here's a pic, and a description of what I did.
"i also made our immersion chiller yesterday. pretty simple. i bought
10 feet of coiled, 1/2 inch, soft copper tubing and two hose clamps
for a total of $14. i also bought a length of washing machine hose,
but i ended up not being able to use it. i took what ended up to be
the outside diameter, and thought it was inside diameter; it didn't
fit over the copper. so i found a length of old garden hose in the
basement, cut it half, and clamped it on to the copper. we'll see if
it works. a couple things i'm a little apprehensive about are that
it's only 10 feet of tube instead of what looks like a lot more in
commercial chillers, and it's 1/8 of an inch bigger than what i've
seen recommended."
Despite those surface area concerns, this thing works pretty well. I can chill 3 gallons in 10 to 15 minutes.
Bryan's chiller has a lot more copper, of smaller diameter. Here's a pic and the description he sent me.
"I built my cooler yesterday, it was a bit more expensive (~$25)than what you
did, but I've got 25' of copper, so I think it'll work pretty well. I actually
bought a kit for installing a dehumidifier or ice maker (~$12) and then some
plastic hose and appropriate couplings, the guy at Home Depot was very helpful,
he practically built it for me."