Commercial Plumbing Cleanout.
There are multiple types of different clean-outs on a commercial application they can be installed on a vertical plumbing stack using a clean-out t which is only acceptable on vertical stacks. or flush with the floor or parking lot with a brass plug sitting recessed to ensure no trip hazard, these can be installed interior or exterior of the structure, they’re normally used to inspect for blockages or to service the plumbing system unclog blockages, etc. You can also clean the plumbing system through event stack on the roof and in some situations this is necessary. they’re also required to be at each change in direction so if you had to reroute a sewer line in the yard around a structure at the change in direction you’re required to install a clean-out.