Special Plumbing Systems: Indirect Waste, Special Fixtures, and Systems
Indirect waste
Indirect waste receptors receive waste from fixtures that must not be directly connected to the drainage system, such as food-handling equipment, sterilizers, and certain medical equipment. The waste pipe terminates with an air gap or air break above the receptor. The receptor must be trapped and vented. Candidates must know the difference between an air gap and an air break.
Special systems
Special systems include medical gas, laboratory waste, fire sprinkler connections, irrigation, and swimming pool piping. Medical gas systems require special qualifications and testing. Laboratory waste may need acid-neutralizing or dilution systems. Pool and spa piping must prevent backflow.
Traps in questions
Watch for direct connections where indirect waste is required, missing air gaps, and improperly trapped receptors. Also watch for questions about which fixtures may discharge to a floor drain.
Worked example
A commercial dishwasher must discharge through an air gap or air break to a receptor. If it is hard-piped directly to the drainage system, the installation is noncompliant because backflow could contaminate the appliance or the water supply.
Rule of thumb
If the fixture handles food, medical items, or chemicals, assume indirect waste is required unless the code states otherwise.