ISO 15749-5:2004

Overview

ISO 15749-5:2004 - Ships and marine technology - Drainage systems on ships and marine structures - Part 5 covers the planning and design of gravity-operated drain lines for grey water from weather decks, non-weathertight spaces, ro‑ro and cargo spaces, and swimming pools. It specifies routing, discharge practices, pipe types and sizing guidance (including a calculation diagram in Annex A) for deck and on-board drainage systems.

Key topics and technical requirements

• Scope and drainage types: Applies to gravity drain lines that convey grey water directly overboard or to bilges (not sewage). Sewage and waste from live animals are excluded and fall under MARPOL and other parts of ISO 15749.
• Discharge rules: Wastewater from exposed decks and open superstructure decks shall be discharged overboard; drains on weather decks should use bulwark openings where possible.
• Drains and fittings: Drains are to be fitted with water discharges without odour seals. Non‑return fittings and shut‑off devices are referenced to ISO 15749-4 where required (e.g., cargo hold overboard outlets).
• Piping materials and joints:
  • Preferred: steel pipes (seamless, welded or threaded) in accordance with referenced ISO steel-tube standards.
  • Spigot and socket steel pipes permitted for exposed superstructure areas; plastic pipes only with classification society approval.
  • Wall‑thickness types (A, B, N) and dimensions are defined depending on installation location (see Tables 2–4).
• Sizing guidance: Typical nominal bore (NB) sizes and indicative drainage capacities (gravity) are given:
  • NB40 = 0.4 l/s, NB50 = 0.7 l/s, NB65/70 = 1.8 l/s, NB80 = 2.6 l/s, NB100 = 4.7 l/s, NB125 = 8.5 l/s, NB150 = 13.8 l/s.
  • Annex A contains a diagram to calculate drainage amount based on pipe width and flow speed.
• Special requirements: Cargo holds on bulkhead decks must clear water at 5° list; refrigerated spaces often drain to bilge via separate lines; collector tanks with level alarms are required if overboard discharge is not possible.

Applications and who uses it

• Target users: naval architects, marine engineers, ship designers, shipbuilders, classification societies, ship operators, and equipment manufacturers.
• Practical uses:
  • Design and layout of deck drainage and pool overflow systems.
  • Selection of pipe materials, nominal bores and wall thickness for drain lines.
  • Ensuring compliance with classification society rules and integration with ship safety/stability calculations.
  • Defining overboard discharge locations to avoid lifeboat or gangway interference.

Related standards

• ISO 15749-1 (sanitary drainage-system design)
• ISO 15749-2, -3, -4 (sanitary drainage for gravity/vacuum/sewage disposal)
• Referenced steel-tube standards: ISO 65, ISO 4200, ISO 9329-1, ISO 9330-1

Keywords: ISO 15749-5:2004, drainage systems on ships, deck drainage, marine structures, drain lines, gravity-operated, swimming pool drainage, cargo space drainage.