What should horizontal drainage piping be equipped with to facilitate maintenance?

Horizontal drainage piping should be equipped with cleanouts to facilitate maintenance. Cleanouts provide access points within the drainage system, allowing for easy inspection, removal of blockages, and maintenance of the pipes. This is crucial because over time, debris and waste can accumulate, potentially leading to clogs or other plumbing issues. By having cleanouts strategically placed in the horizontal piping, a plumber can effectively maintain the system without the need for extensive disassembly or disruptive interventions.

Other options, while important in specific contexts within plumbing systems, do not serve the same purpose as cleanouts. Shut-off valves are primarily used to control water flow, water traps are designed to prevent sewer gases from entering the building, and vent pipes ensure that the drainage system is adequately aerated. None of these fulfill the maintenance role that cleanouts provide in dealing with drainage piping.