Standing water trapped in the drain line can grow mold or bacteria, leading to a musty smell. Why Does the Drain Get Blocked? Two main culprits usually cause a backup:

Ensure your freezer isn't set too cold, which can cause the drain line to freeze.

In bottom-freezer models, the water may freeze into a solid slab before it can leak out.

Modern frost-free refrigerators and freezers cycle through a defrost mode to melt ice off the evaporator coils. The defrost water drain is the exit path—a small hole (usually inside the back wall of the fridge) that channels this melted water out of the冷藏室/冷冻室.