Drainage stacks that receive wastes from sinks, automatic dishwashers, laundry trays, laundry washing machines, and similar fixtures shall have the drainage and vent piping so arranged that suds pressures will not affect fixtures in the lower portion of the drainage system. No fixture drain, branch, or branch vent shall connect to any stack in a suds pressure zone. Such zones shall be considered to exist at any offset of 60 degrees to 90 degrees or at the base of any drainage.