The admission into the public sewers of any waters or wastes in volumes, or with constituents, such that existing dilution conditions in the sewers or at the treatment plant would be adversely affected, shall be subject to review and approval of the director. Where necessary, in the opinion of the director, pretreatment or equalizing units may be required to bring constituents or volume of flow within an acceptable level, and to hold or equalize flows so that no peak flow conditions may hamper the operation of any unit of the sewer system. The equalization or holding unit shall have a capacity suitable to serve its intended purpose, and be equipped with acceptable outlet control facilities to provide flexibility in operation and accommodate changing conditions in the waste flow.