Boiler relief discharge must dump to indirect waste via an air-gap. Which option describes this method?

• A. Direct to sewer
• B. To the building drain
• C. To indirect waste via an air-gap
• D. To stormwater

Answer: (C)

Boiler relief discharge must be kept from directly entering the sanitary or potable-water systems, so it’s protected by an air-gap that creates a physical barrier. The best way to do this is to route the relief discharge into an indirect waste receptor and keep the discharge separated from the sanitary piping by an air-gap. The air-gap ensures that if backflow or siphoning occurs, wastewater can’t be drawn back into the building’s water supply or interior piping. From that indirect waste receptor, the wastewater then flows to the sanitary sewer as designed.

Discharging directly to a sewer or to the building drain bypasses this protective gap and the backflow-prevention intent, which is why those methods aren’t acceptable. Connecting to stormwater is not appropriate for boiler relief because it isn’t part of the building’s sanitary waste system and could create environmental and code issues. The air-gap (typically a small, clearly measurable vertical separation) provides a simple, reliable safeguard that aligns with standard plumbing practice for safety relief discharges.