Bilge Water Management
Bilge discharges: geographical conditions, OWS, alarm and automatic stopping, checks and records.
Operational Explanation
Machinery-space bilge water may contain oil from leaks and washings. For ordinary discharges under regulations 15.2–15.3, effluent must pass through the required equipment and not exceed 15 ppm without dilution. Below 400 GT, the separate regulation 15.6 branch applies; geographical prohibitions remain decisive.
The equipment fitted depends on tonnage, and the split is finer than the usual summary. For ships of 400 GT and above but below 10,000 GT, Regulation 14.6 asks only for equipment “of a design approved by the Administration” ensuring that the effluent does not exceed 15 ppm: that paragraph mentions neither the alarm nor the automatic stopping arrangement. Alarm and automatic stopping are both in Regulation 14.7, which applies to ships of 10,000 GT and above and which adds to the text of 14.6 an “alarm arrangement to indicate when this level cannot be maintained” together with the automatic stopping provisions.
Read the actual configuration in the approved design, IOPP Supplement and manuals. MEPC.107(49) covers separator, alarm and stopping where applicable: below 10,000 GT neither presence nor absence of automatic stopping can be inferred.
Equipment is only half the condition. Regulation 15 also requires the ship to be proceeding en route: a discharge carried out at anchor or alongside is not compliant even if the effluent is below 15 ppm. The PSCO may compare records with available navigation data.
For ships of at least 400 GT, outside polar prohibitions, regulation 15.3 permits Special Area discharge under its cumulative conditions, including 14.7 equipment. Ordinary discharges of oil or oily mixtures are prohibited in Arctic waters and the Antarctic area; restricted regulation 4 exceptions remain. See polar-water discharges.
Regulatory Reference
MARPOL Annex I: MEPC.117(52), regulations 14, 15 and 17, with MEPC.265(68) and Polar Code MEPC.264(68), II-A 1.1. Specifications MEPC.107(49), 1.3: ships with keels laid from 1 January 2005 and new installations from that date on older ships, so far as reasonable and practicable. Check applicable standards for older equipment, without imposing universal retrofitting.
Alarm: MEPC.285(70), amendment to 4.2.11. Certificates checked at annual, intermediate and renewal IOPP surveys; accuracy verification by calibration and testing performed by the manufacturer or a person authorised by the manufacturer, at intervals not exceeding five years from commissioning and subsequently from the last check, or the manufacturer’s shorter prescribed interval; alternatively replace with a calibrated unit. Keep certificate on board. Functional testing and separator maintenance do not replace alarm calibration.
Scope of Application
Regulations 14.6–14.7 distinguish 400–9,999 GT from 10,000 GT and above, subject to the special conditions and approved waivers in 14.3–14.5, including retention. Regulation 15.3 concerns ships of at least 400 GT. Below 400 GT, separate regulation 15.6 applies: retention or discharge under its conditions and arrangements accepted by the Administration. Equipment waivers do not cancel geographical prohibitions.
Procedure / How to Complete It
- Check area and regime first: no ordinary discharge in Arctic waters or the Antarctic area.
- Check approved equipment, functional test, maintenance and alarm calibration certificate with date and applicable interval.
- Regulations 15.2–15.3: proceeding en route, undiluted effluent not exceeding 15 ppm, required filtering, no cargo pump-room bilges and, on oil tankers, no mixture with oil cargo residues. In Special Areas verify 14.7; below 400 GT use 15.6.
- Monitor under the manual: do not infer stopping from tonnage. On alarm or failure, stop discharge and retain on board without bypass.
- ORB: D 13–15 for non-automatic starting with required quantity, times, method and positions; E 16–18 for automatic starting without invented volumes; F 19–21 for equipment condition/failure, restoration and reason, with other applicable guidance entries. Maintenance is not automatically an F failure.
Practical Example
Code E has no volumes. In the Oil Record Book Part I, in the sections replaced by resolution MEPC.187(59), code (E) is titled “Automatic starting of discharge overboard, transfer or disposal otherwise of bilge water which has accumulated in machinery spaces” and has three items: 16 “Time and position of ship at which the system has been put into automatic mode of operation for discharge overboard, through 15 ppm equipment”; 17 the time the system was put into automatic mode for transfer to a holding tank, with the tank identified; 18 the time it was put back into manual operation.
The quantity lives under code (D), item 13: “Quantity discharged, transferred or disposed of, in m3”, with item 14 for the start and stop times and item 15 for the method — and 15.1, where the discharge is through the 15 ppm equipment, asks for the position at start and end. The titles of the two sections are also more precise than the usual shorthand: they speak of starting, that is the non-automatic or automatic initiation, not of the discharge itself.
Training entries for two alternative scenarios. For ships holding an IOPP Certificate, entries must be at least in English, French or Spanish (Regulation 17.4). Code E, item 16: "03-AUG-2026 22:10, system put into automatic mode of operation for discharge overboard through the 15 ppm equipment, position 41°12'N 010°05'E"; item 18: "04-AUG-2026 01:35, system put back into manual operation". Code D, for a manually started discharge: item 13 "4.2 m³"; item 14 "start 03-AUG-2026 22:10, stop 04-AUG-2026 01:35"; item 15.1 "through 15 ppm equipment, position at start 41°12'N 010°05'E, at end 41°44'N 010°31'E". Officer in charge’s signature on each entry.
What Typically Goes Wrong
Common Mistakes Mistake Library
| Mistake | Consequence | How to avoid it |
|---|---|---|
| Confusing functional testing with alarm calibration | Equipment response may appear correct without a documented check of measurement accuracy | Check functional testing/maintenance separately from the calibration certificate; use the applicable interval or the manufacturer’s shorter interval |
| Inferring automatic stopping from tonnage alone | An unverified safeguard may be relied on in the actual configuration | Read the approved design, IOPP Supplement and manual; verify the alarm and automatic stopping where fitted, including below 10,000 GT |
| Treating 15 ppm as permission to discharge in any area | A discharge may remain prohibited even below the effluent limit | Check the area and regulation 15 branch first, then every cumulative condition, including proceeding en route |
| Omitting applicable ORB fields or treating volumes as required code E fields | The entry does not correctly reconstruct the starting, operation or failure | Select D 13–15, E 16–18 or F 19–21 for the case and complete the required particulars, as in the examples |
What the PSCO Checks
Operational Tips
- Maintenance and monitoring under approved manual and SMS.
- Do not ignore alarms: verify automatic stopping where fitted in the approved configuration, including below 10,000 GT.
- Document maintenance and replacements; retain the alarm certificate.
Preparation checklist
Educational checklist. This summary supports learning and preparation only. It does not replace the vessel’s approved procedures, manuals, statutory documents, company SMS, or applicable official requirements. Completing it demonstrates neither compliance nor readiness for an inspection: it shows that a list has been read, not that the ship is in order. Always verify the current documents carried on board.
- Check area and regime first: no ordinary discharge in Arctic waters or the Antarctic area.
- Check approved equipment, functional test, maintenance and alarm calibration certificate with date and applicable interval.
- Regulations 15.2–15.3: proceeding en route, undiluted effluent not exceeding 15 ppm, required filtering, no cargo pump-room bilges and, on oil tankers, no mixture with oil cargo residues. In Special Areas verify 14.7; below 400 GT use 15.6.
- Monitor under the manual: do not infer stopping from tonnage. On alarm or failure, stop discharge and retain on board without bypass.
- ORB: D 13–15 for non-automatic starting with required quantity, times, method and positions; E 16–18 for automatic starting without invented volumes; F 19–21 for equipment condition/failure, restoration and reason, with other applicable guidance entries. Maintenance is not automatically an F failure.
FAQ
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Certified substantive revision: 16 October 2026 · page fingerprint 6e8c991b1426