It is illegal and therefore never acceptable to use a compression fitting to repair a broken brake line. Instead, a flared fitting should be used. Automobile inspection offices or stations forbid the use of a compression fitting in brake line repairs. Vibrations and the mere stress of the brake system can lead to the compression fittings becoming unstable over time and causing a severe leak. It is for this very reason that using a compression fitting is illegal in repairing a brake line. A flared fitting is a relatively inexpensive and easy legal alternative which is generally considered to be a much safer and more permanent repair for a broken brake line.