Trap Primer Sizing

ScopePrimer / distribution-unit count, annual water use, and an IPC 1002.4 occupied-space compliance check for floor-drain trap seals. Manufacturer flow rates govern.

Formula or tableprimers = ceil(floor-drain count / drains-per-distribution-unit). Annual water = drains × (delivery oz per cycle / 128) × cycles per day × 365. Trap seals subject to evaporation, and emergency floor drain traps, are protected by one of the IPC 1002.4.1.1-1002.4.1.5 methods.

Source and editionIPC 2027 (International Plumbing Code). Section 1002.4 (trap seal depth) and 1002.4.1 (trap seal protection). Manufacturer flow rates per published cut sheets (Precision Plumbing Products / Sioux Chief / Mifab).

Free accessFree read-only access at codes.iccsafe.org.

What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.

API field namesfloor_drain_count, zone, prime_method, prime_volume_oz, cycles_per_day, primers_needed, water_gal_per_year

• Drains per distribution unit 4 for electronic / pressure-drop / pump-discharge; 1 for manualPPP / Sioux Chief / Mifab distribution-unit cut sheets
• Default delivery 8 fl oz per cycle, one cycle per day, unless the user enters the manufacturer valuemanufacturer cut-sheet typical
• Protection rule an emergency floor drain trap, or any trap seal subject to evaporation, needs one of the 1002.4.1 methods (a potable-water or reclaimed-water primer valve, a wastewater-supplied primer device, an ASSE 1072 barrier device, or a lavatory or hand-sink drain connection); manual priming is not one, and the code has no mechanical-space exceptionIPC 2027 §1002.4.1 (unchanged from 2021)