USAF Mobile Water Supply (MWS) Fire Practice Test 2026 - Free MWS Fire Practice Questions and Study Guide

Water left in piping, pumps, and booster lines can freeze when temperatures drop during storage. Ice expands, and that expansion inside pipes and fittings creates internal pressure that can crack, split, or burst components and damage seals or pump housings. Draining removes the water from these lines, so there’s nothing to freeze and form ice plugs or cause damage. While minimizing moisture can help with corrosion over time, the immediate and primary reason for draining before storage is to prevent freezing. The other options don’t address that freezing hazard directly—reducing wear isn’t the main concern, draining doesn’t raise pressure, and rust prevention is a longer-term issue.