Installing clean outs can be one of the most efficient things you can do for your future plumbing backups. A clean out is a 3-4 inch PVC pipe connected to your sewer line with a threaded cap that can be opened, when access is needed. When having a clean out installed, you need to make sure that it is a two-way clean out. A two-way clean out makes sure that the serviceman can run the cable both toward the house and toward the street or septic tank to properly clean your line. Pictured Left is an example of a properly installed clean out.