How to Build a Side-arm Heat Exchanger

Insert about 3 inches of one end of the large diameter copper tube into a vise then gently tighten the vise until the tube is secure but not crushed.

Bend a 90-degree angle in the copper tube where it meets the vise. Try to avoid kinking the tube; however, if a kink does occur, it is generally fine. The biggest problem a kink will present is a leak in the larger tube.

Remove the copper tube from the vise and turn it around before re-inserting the other end into the vise. Bend another 90-degree angle in the copper tube. Generally, you will make the 90-degree bends so that the ends are parallel and in the shape of a Z or a U, but you should make the shape appropriate for your application.

Set the thin-walled copper tube along the central portion of the large tube, about 3 inches from the end and against the end of the large tube clamped in the vise.

Bend the small tube down and around the central portion of the larger tube.

Continue bending the small tube around the central portion of the larger tube into a tight coil with the small tube always in contact with the larger tube.

Remove the larger tube from the vise and you have a simple side-arm heat exchanger.