What are the main causes of sewer line blockages?

The primary causes of sewer line blockages involve several specific factors, with accumulation of grease, root intrusion, foreign objects, and sediment being the most significant. Grease and fats poured down drains can solidify and build up over time, leading to significant clogs. Roots from trees can infiltrate sewer lines through small cracks, causing blockages that can be difficult to remove. Foreign objects, such as wipes or other non-biodegradable items, can obstruct the flow of sewage. Additionally, sediment can accumulate in the pipes, particularly in older systems or those that are poorly maintained, contributing to blockages.

Heavy rainfall and flooding can lead to temporary surcharges but are not direct causes of persistent blockages. Improper construction may result in structural issues that can predispose a system to blockages but are not typical causes of blockages once the system is operating. Excessive water flow from treatment facilities may impact the hydraulic capacity of the pipes but does not directly lead to blockages like the factors listed in the correct answer. Thus, the accumulation of grease, root intrusion, foreign objects, and sediment directly relates to the common causes of sewer line blockages, making this choice the most accurate representation of the issue.