Begin by completely draining all remaining coolant. Residual fluid can corrode the tank's interior, especially if it contains water or degraded additives. Tilt the tank to empty every last drop, then rinse it with distilled water to remove leftover contaminants. Allow it to air-dry thoroughly—trapped moisture can lead to mold or rust, particularly in metal tanks.

Thoroughly inspect the tank for cracks, worn seals, or loose components. Repair minor issues with appropriate sealants or replacement parts before storage; unresolved damage may worsen over time. For plastic tanks, avoid flexing or stacking heavy items on top, as this can cause warping.

Select a storage location that is cool, dry, and away from direct sunlight. Extreme temperatures (both hot and cold) can degrade plastic or rubber parts, while humidity promotes corrosion. A garage shelf or covered storage unit works well. If space is limited, store the tank upright to maintain its shape, and avoid contact with chemicals or sharp objects that might scratch or puncture it.