When drains are well kept, they perform their function efficiently by transferring wastewater smoothly. They help with proper disposal, removing dirt and grease from the kitchen and bathroom sinks.
When maintenance is neglected, the lining of the drainpipes sees a thick deposit of grease and other substances that have built up over the course of time. Due to these particles collecting on the surface of the walls, the diameter of the pipe becomes smaller and resists the smooth flow of wastewater. Not only this but with time the transmission of water can be completely reduced, causing the wastewater to back up. When this happens, you experience a very unpleasant emergency.
The good thing is that there are signs that foreshadow the occurrence of such an emergency, and you could use those signs to avoid such a disaster altogether. Slowly draining or standing water is a sign of a clog being present in the pipe. A foul odor emanating from the drain either outside or anywhere near the sink/toilet inside the home is also an obvious sign of blockage.