The answer to 'why is my sink burst pipe' is that a burst pipe under the sink is usually caused by a blockage, excessive water pressure, or freezing temperatures. Symptoms include water leaking from the sink cabinet, low water pressure, or the sink draining slowly. Solutions may involve unclogging the drain, repairing or replacing the pipes, or insulating exposed pipes to prevent freezing.
If the burst pipe is a simple clog or small leak, you may be able to fix it yourself with basic plumbing tools and supplies. However, for larger issues like major pipe damage or a complex plumbing system, it's best to call a professional plumber. They have the expertise and equipment to properly diagnose and repair the problem to prevent further water damage.