What potential issue can arise from improperly installed horizontal drains?

Improperly installed horizontal drains can lead to blockage and backup in the plumbing system. This situation occurs mainly due to poor slope and alignment of the pipes. When horizontal drains are not sloped correctly, waste and sewer flow can become sluggish, causing materials to settle and accumulate instead of flowing freely. This buildup can create significant clogs over time, resulting in backups that may affect the entire plumbing system, leading to unsanitary conditions and potential damage to property.

Additionally, while other issues such as odors, leakage, and pressure problems can occur in plumbing systems, they are not as directly connected to the specific installation of horizontal drains as blockage and backup are. Proper installation with the right slope is critical to ensure that gravity can effectively carry waste away, preventing the types of problems that arise from blockages.