backflow

noun backflow

• wane — to decrease in strength, intensity, etc.: Daylight waned, and night came on. Her enthusiasm for the cause is waning.
• sweep — to move or remove (dust, dirt, etc.) with or as if with a broom, brush, or the like.
• abatement — Abatement means a reduction in the strength or power of something or the reduction of it.
• decrease — When something decreases or when you decrease it, it becomes less in quantity, size, or intensity.
• flagging — becoming smaller or weaker; dwindling.