The bladder‑type water hammer arrestor is typically installed downstream of the check valve at the pump outlet of a water transmission pipeline. It is an active protective device that prevents both pressure rise and pressure drop water hammer. 

When a pump trip occurs due to power failure, the initial pressure inside the arrestor forces high‑pressure water from the bladder into the downstream pipeline. This replenishes the line and reduces the pressure drop depth caused by pump‑stop water hammer, thereby suppressing negative pressure at the source and preventing potential column separation and subsequent rejoining water hammer. When a returning pressure rise water hammer arrives from the downstream pipeline, the compressed gas inside the bladder‑type arrestor is further compressed, smoothing out the peak pressure surge.