This safety alert warns people about the risks of becoming trapped and drowning at drainage or pipe inlets.

An example of guarding that can be used to minimise the risk of entrapment.

A worker recently drowned after becoming trapped at the inlet of a 300 mm water pipe. The purpose of the pipe was to remove water from an open water retention area at an industrial site.

During a heavy storm the pipe became blocked with debris. A worker, attempting to clear the debris, was sucked into the pipe, became trapped, and drowned under rising water.

Contributing factors

An inlet pipe similar to the one involved in the incident.

There was no barrier in place to prevent someone from becoming trapped in the pipe.

Other contributing factors were:

  • Workers being unaware of the strong suction forces created in the pipe.
  • The design of the drain allowed a suction force sufficient to trap a person.
  • Clearing debris from the drain involved workers manually removing it.
  • Instructions and procedures that prohibited workers from entering water above gumboot height were not followed, resulting in  the worker becoming trapped.

Action required

Systems of work should be reviewed when water or other fluids flow into an inlet pipe and there is potential to trap and drown someone.

Action is warranted when:

  • a person may be trapped against (or in) an inlet pipe by suction forces, which can be caused due to gravity – eg stormwater or flow from a tank – or plant – eg a pump
  • the size of the pipe inlet is sufficient to trap and hold a body part – eg hand, foot, leg, arm, torso, head
  • the inlet can flood to a depth sufficient to cause drowning – eg in retention areas, where water or liquid levels increase due to storms or drainage blockages, such as a process tank, pool, dam, river or pit.

Where  entrapment and drowning hazards exist, conduct a risk assessment of the site to identify risks, then eliminate or, if not reasonably practicable, minimise the risks. Control measures may include:

  • a barrier – eg  grate, guarding fencing – designed by a competent person, to prevent people from accessing, becoming trapped or held against an inlet pipe, or being pulled into or through pipework
  • a system that relieves the entrapping suction or shuts down the pump when a blockage is detected (if a barrier is not reasonably practicable)
  • relevant instruction, information, training and supervision on safe access and dangers associated with drains or inlet pipes
  • water depth gauges and signage warning of the risk of entrapment and drowning
  • bollards (posts) in an arc upstream of the inlet pipe, so the inlet can be identified when flooded.
  • safe work procedures for using, accessing and maintaining drains and pipes, particularly when working near pools of water

Further information

Call us on 13 10 50 or visit where you will find the How to manage work health and safety risks code of practice.

You might also find chapter 12 of the Queensland Urban Drainage Manual 2013 useful.

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