MARPOL Annex IV - Sewage Holding Tank Capacity
Required black-water holding tank capacity from persons on board, daily generation rate and longest no-discharge segment.
Daily generation
1.25m³/day
Required holding capacity
4.31m³
Formula, assumptions, and limits
V_tank in cubic metres, N persons, q litres per person per day, t no-discharge days, k reserve factor (typically 1.1 to 1.2). Default q is 50 L/person/day per IMO MEPC.115(51) commentary; cruise ships typically 65 to 90 L/person/day. The longest no-discharge segment is the worst-case time between reception facility access plus operations within 12 nautical miles of nearest land. Holding tank size is also constrained by ship structural and weight considerations.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Persons on board | persons | safety certificate | |
| Generation rate per person | L/person/day | operator estimate | |
| Longest no-discharge segment | days | voyage plan | |
| Reserve factor | multiplier | operator policy | |
| Required holding capacity | m³ | computed |