Most experts will recommend having sewer lines inspected prior to purchasing or renting a new home to be sure that there are no issues the buyer might be unaware of. Periodic cleaning of sewer lines can also help prevent clogs and backups in the sewer drains - a headache no one wants to deal with. If the home has a history of lines draining slowly, it's a good idea to have them inspected and cleaned before a major clog happens. In addition, homes that are more than forty years old are probably due for a cleaning even if the drains appear to be functioning normally. Other environmental factors can affect the sewer lines as well, such as penetration by tree roots underneath the property. Grease, hair, food, and other blockages can also gradually build up over time and cause a major sewer clog. Signs of trouble include slow drains, foul smells, gurgling pipes, or water pooling around toilets and bathtub drains. Because these things happen beneath the ground, it's difficult to monitor or even know that there could be an issue without having the line inspected periodically.