It is helpful to understand the basics of how a sewer system works when you have plumbing problems. These details can give you a better idea as to what the issue actually is when you experience a problem.All of the drains in your home connect to branch lines that travel to the main line, which is also known as the main stack. This includes the drains from your sinks, bathtubs, showers, washing machine, dishwasher, utility tubs, and toilets. The main line exits your home near its foundation and runs toward its connection with the city's sewer system. Your main sewer pipe funnels the waste water into the city's sewer line. If you don't have public sewer lines, the main line travels to your septic system.The entire drainage system works through gravity. The waste water runs downhill through sloped drain lines. Each branch line funnels waste into pipes that become increasingly larger in diameter as they run closer to the main line. Once the waste water enters the main line, it is funneled into the sewer system. Each drain pipe is also connected to a vent system opening to the outside of your structure. This system allows air to enter the drain pipes, enabling the free flow of the waste water. The vent system also allows odors and gases to escape into the atmosphere. Both your drain and vent lines must be clear in order to maintain the proper level of pressure and flow within your drain lines. Plumbing vent pipes are also referred to as vent stacks. They are largely vertical pipes that connect to a main vent, which typically exits through the roof of your home. The openings of the vent pipes must be kept clear of debris. Debris entering your vent stack can lead to clogging and inhibit proper air flow. If the flow of air is restricted or cut off, the flow of waste water can slow down or stop completely, resulting in the symptoms of a clogged drain line, even if the drain itself is completely clear.