There are a number of common culprits that cause blockages in drains, including:
Accumulation of hair, soap scum, and debris in bathroom and the shower drain
Food scraps, grease, and cooking oil buildup in the kitchen sink.
Tree roots infiltrating and clogging sewer pipes.
Foreign objects, such as sanitary products or toys, getting lodged in the pipes.
Sediment and debris accumulation in stormwater drains