Trap Primer Sizing

Primer / distribution-unit count, annual water use.

Run the calculator

Example

You enter

Floor-drain count 6
Building zone occupied
Prime method electronic
Delivery per cycle (fl oz) 8
Prime cycles per day 1

You get

Primers needed 2
Annual water use 136.9 gal/yr

Details, formula, and sources

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

primers = ceil(floor-drain count / drains-per-distribution-unit). Annual water = drains × (delivery oz per cycle / 128) × cycles per day × 365. Occupied-space floor drains require a primer per IPC 1002.4.

IPC 2021 (International Plumbing Code). Section 1002.4 (trap seals). Manufacturer flow rates per published cut sheets (Precision Plumbing Products / Sioux Chief / Mifab).

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

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

Field names used by the API: floor_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
Occupied-space rule every floor drain in occupied space requires a primer; manual prime allowed only in mechanical spaces with a documented seasonal procedureIPC 2021 §1002.4 and exception