Which statement correctly describes how copper tubing is joined based on location (indoor vs buried)?

• A. indoors solder joints; buried flare/compression
• B. indoors flare/compression; buried solder joints
• C. indoors solder joints; buried solder joints
• D. indoors compression; buried flare

Answer: (A)

When joining copper tubing, the method is chosen based on accessibility and safety. Indoors, solder (sweat) joints are common because you can safely use a torch in a controlled, accessible environment to fuse the copper with flux, producing a strong, leak-tight seal for piping inside buildings.

For buried lines, heat cannot be applied in the soil, and the joint must resist moisture, soil movement, and backfill conditions. Therefore, flare or compression fittings are preferred because they seal without flame and can tolerate slight shifts or settling underground. A flare joint forms a seal with a flared tube end and nut, while a compression joint uses a ferrule and nut to tighten and seal around the tube.

So, indoor piping is typically joined with solder joints, while buried service lines use flare or compression joints.