Below-grade washouts on must be sized to contain all liquid and solid waste you expect to generate in between cleanout periods. On larger sites, the pit should be at least 10 feet wide by 10 feet long and accommodate a minimum 12 inch freeboard (safety margin) in the sizing calculations...
and 12 inches on smaller pipes. Concealed cleanouts shall be provided with access of sufficient size to permit removal of the cleanout plug and rodding of the system. Cleanout plugs shall not be concealed with any permanent finishing material. Fixtures having concealed tubular traps shall be pro...