What can happen when a plumbing system is not properly vented?

When a plumbing system is not properly vented, it can create vacuum conditions within the drainage system. These vacuum conditions can hinder the drainage of wastewater, leading to incomplete drainage or slow draining fixtures. Additionally, the lack of adequate venting can cause siphoning effects, where the water in traps is drawn out, allowing sewer gases to enter the living space. Proper venting is essential to maintain atmospheric pressure within the plumbing system, which ensures that wastewater flows freely and traps remain filled with water to prevent foul odors from escaping. Thus, the consequence of inadequate venting emphasizes the importance of maintaining proper ventilation to ensure efficient and safe drainage.