What causes drain to gurgle when sump stops running?

A gurgling drain when a sump pump stops running is typically caused by air being drawn into the drainage system. When the pump turns off, a drop in pressure can create a vacuum effect, pulling air through the water in the pipes. This disturbance can lead to the characteristic gurgling sound as the air bubbles rise through the water. Additionally, it may indicate a partial blockage or improper venting in the drainage system.