I use vinyl hose, 3/8 id, 1/2 od. The stuff is dirt cheap, I bought 30ft for $7.50.. Still haven't used half of it, and I've completely replaces all the hose in my system several times. On my first setup, I ran that thing for over 4 months without changing the hose. It did become stiff, but never had a hose related leak.
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The UnaClocker
Overclock till it goes BOOM!
Watercooler extraordinaire!