What must be done to ensure proper drainage in a plumbing system?

To ensure proper drainage in a plumbing system, it is crucial that the piping is installed with the correct slope. This sloping is essential because it allows gravity to assist in moving wastewater through the pipes, thereby preventing clogs and ensuring effective drainage. Typically, a slope of a quarter inch per foot is recommended for drainage pipes to facilitate smooth flow and proper evacuation of wastewater.

If the piping is not sloped correctly, even a slight dip in the pipes can cause water to pool, leading to blockages or backups in the system. Furthermore, without appropriate slope, the materials carried in the wastewater may settle along the bottom of the pipe, creating further obstruction over time.

The other options do not directly contribute to the primary requirement for effective drainage. While having all fixtures at the same height might seem logical, it does not account for the necessary action of water flow and drainage via gravity. Only using metal pipes does not inherently improve drainage since drainage relies on the slope and routing of pipes, not just the material. Installing additional pumps may be a solution in some cases to assist with drainage issues, but it is not a standard requirement for ensuring proper drainage in a well-designed plumbing system.