Clay sewer lines are the most likely kind of pipes to develop hairline cracks. These cracks can be caused by a range of different factors. They can form anywhere in the pipe—on the top, bottom or sides—and can spread to affect the entire circumference. We at Safe Investment Home Inspection will recommend that you keep an eye on hairline cracks if we find them during your sewer inspection. Usually, they don’t pose any issues right away and they are not dire enough to require immediate fixing. However, hairline cracks can turn into more serious problems if they get larger and lead to a completely broken pipe. It’s best to get your sewer lines looked at again every four to six years if hairline cracks are found so the condition of the cracks can be monitored for changes.