Safety update

February 1997 Failure of non return valves causes capsize

This safety update is for all seafarers. It is issued to raise awareness of the potential serious risk to safety on board a vessel where non return valves malfunction. It provides safe practice tips for how best to reduce the risks involved and to alert people to the risk to safety associated with non return valves.


Seafarers are warned to pay attention to non return valves following the sudden capsize of a fishing trawler and drowning of a deck hand.

Information on non return valve malfunction

Maritime New Zealand’s investigation report states that the capsize was caused by a loss of stability due to back-flooding of the fish hold via the vessel’s bilge pumping system. The flooding of the fish hold was caused by the malfunction of three non return valves in the bilge pumping system. Although a policy relating to the need for non return valves to be closed when not in operation was communicated to all skippers by company management, this policy was not adhered to on this occasion.

Safe practice tips

The report recommends, among other things, that:

  • Personnel who operate non return valves in the engine room should be aware that these valves can be prone to malfunction.
  • The maintenance staff ashore and afloat carry out regular checks and maintenance on non return valves.
  • Skippers and engineers note the dangers of free surface effect.

Original source content - Boat Notice 051997, February: Failure of non return valves causes capsize.

Email updates

Get an email notification when a safety update is available online.


Contact us for more help

If you have any questions about this safety update, please contact our Wellington office.


New Zealand (toll free):
0508 225 522

Call Maritime New Zealand now

Tell us what you need help with and remember to include your contact details (email address and phone numbers).