Key Concept: Sudden flow changes in a pipeline can cause 'water hammer' — a damaging pressure spike.
Why it's correct: A surge tank acts as a buffer that absorbs these sudden pressure fluctuations, protecting the pipeline from damage and keeping pressure steady.
Why others fail: Storing excess water is a reservoir's job, removing air is an air-relief valve's job, and increasing velocity is a pump's job — none of these is what a surge tank does.