All cleanouts should be accessible or reachable without having to remove a permanent portion of the structure. Cleanouts are designed to make the interior of a drainage system accessible for clearing stoppages without inconvenience, dismantling wall or ceiling finishes, or disturbing the sanitary drainage system. Cleanout plugs are very common. They are usually located at changes in direction in a drain line and at the bottom of stacks. Cleanouts should be installed to open and allow cleaning in the direction of the flow of the drainage pipe, or at right angles thereto. They must be water-tight and gas-tight. A cleanout plug can be made of brass or plastic. A cleanout plug should have a raised square or a counter-sunk square head where a trip hazard may exist. The square shape minimizes the possibility of stripping the plug during removal.
Drainage pipe cleanouts should be installed not more than 100 feet apart in horizontal drainage lines, as measured from the upstream entrance of the cleanout.
A cleanout should not be covered with cement, plaster or other finish material. Where it is necessary for a cleanout to be concealed, an approved type of cover plate or access door should be provided. The minimum clearance in front of cleanouts should be 18 inches (457 mm) on pipes 3 inches and larger, and 12 inches (305 mm) on smaller pipes.
Cleanouts should be installed at each change in direction greater than 45° (0.79 rad) in the building sewer, building drain, and horizontal waste or soil line. A cleanout is not required for each and every change in direction. If a 90°-change in direction is made with a single fitting, then a cleanout is needed. If the same change in direction is made with two bends, a cleanout is not required because rodding equipment should be able to easily pass through fittings having a change in direction of 45° or less. www.nachi.org