Tubing is replaced (partially or entirely) when:
- threaded connections are badly worn letting compressed gas (air) into the string,
- holes, cracks, cavities or corrosion are detected on the tubing body,
- salts and paraffin are deposited on the inner surface of the pipes and they cannot be removed without tubing POOH,
- the tubing diameter needs to be reduced or increased, tubing configuration or design is to be changed.