Blockages are most often caused by excessive buildups of grease (a result of pouring cooking grease and fat down the kitchen sink). When flushed, plastic and other non-soluble materials such as baby wipes, diapers, feminine products, and kitty litter can also get caught in the line and block the flow of wastewater through the system. Tree and shrub roots that have grown into the line are also a common problem. Sanitary sewer lines installed prior to 1980 in Nassau and Suffolk Counties are primarily made of cast iron or clay and can deteriorate or become brittle over time. Roots seek water and will find their way through cracks and holes causing blockages and further damage. Unfortunately, contractors can also cause damage to sewer lines due to inexperience and improper tool usage.