Air Admittance Valve Installation Check (IPC 918)

at least one vent pipe must still extend to the OUTDOORS. A valve admits air to relieve NEGATIVE pressure and does nothing about POSITIVE pressure -- the air a discharging stack pushes ahead of it needs a path out, and a building vented entirely on valves has none. No amount of correct placement fixes that. The rest is placement and capacity: not less than 4 in above the branch or fixture drain served (918.4), not less than 6 in above insulation (918.6), in a VENTILATED space, ACCESSIBLE because a diaphragm eventually fails, and rated in DFU per its ASSE 1051 or 1050 listing (individual, branch, and stack types are not interchangeable). Whether AAVs are permitted at all is the first question and varies by jurisdiction.

pass requires an outdoor vent present, a ventilated space, accessibility, height above the branch or fixture drain >= 4 in, height above insulation >= 6 in where insulation is present, and a valve DFU rating >= the DFU served where both are entered.

IPC 918 - air admittance valves located not less than 4 in above the horizontal branch drain or fixture drain being vented (918.4), installed not less than 6 in above insulation materials (918.6), located in a ventilated space and remaining accessible, and at least one vent pipe extending to the outdoors even where air admittance valves are used (918.7).

The placement and outdoor-vent provisions are short prescriptive sentences reproduced in municipal adoptions, ICC CodeNotes, and manufacturers' free code summaries. No table is reproduced; the valve rating is read from its own listing.

Estimate. AHJ and licensed professional govern.

Field names used by the API: height_above_drain_in, height_above_insulation_in, has_outdoor_vent, ventilated_space, accessible, dfu_served, valve_dfu_rating, drain_deficit_in, insulation_deficit_in, dfu_margin

• Outdoor vent still required at least one vent pipe to the outdoors even where AAVs are usedIPC 918.7
• Height above drain not less than 4 in above the branch or fixture drain being ventedIPC 918.4
• Height above insulation not less than 6 inIPC 918.6
• Ventilated and accessible a sealed cavity starves the valve; a buried valve cannot be replacedIPC 918
• Capacity DFU rating from the valve's ASSE 1051 / 1050 listing; types are not interchangeablevalve listing
• Permission whether AAVs are allowed at all varies by jurisdiction and is not checkedstated scope limit