A fellow brewer here made a really cool contra-flow chiller. Inner pipe has wort, outter pipe has water. It cuts down on water wastage, he says.

Whatever, it looks cool and is a fine piece of oxyacetylene brazing and tube bending. I guess it's 1" ID outter and 1/2" OD inner, both copper. The total length looks like maybe a couple of yards or so and coiled about 1/2 ft radius. He runs tap water through the jacket using rubber tube nipples on both ends and gravity feeds the wort. I don't know how he keeps the tubes symmetrical and not touching. Too thick-headed to ask.