STA POOL PLANT – ENTRAPMENT & ENTANGLEMENT
Suction Entrapment And Hair Entanglement With incidents involving hair entanglement and suction entrapment still happening around the world, in this issue, Robbie Phillips, STA’s Pool Plant Technical Advisor, raises the issue again to warn operators about the dangers of both, with a view to preventing such incidents going forward
W
e often see the subject of suction entrapment featured in the news here in the UK and abroad, many times because of tragic circumstances; it is therefore important as pool operators that we keep reminding ourselves of the risks involved, and what we need to do to mitigate them, and what checks we need to have in place. The facilities include commercial pools, hydrotherapy pools, wading / paddling pools, interactive water features, hot tubs and spa baths. Also, add on features with separate pumping, all have one thing in common – a water circulation system(s). This means that water must leave the pool and then re-enter at another point following filtering and disinfection. This in turn means water under suction from the facility. If not properly managed then this can have serious repercussions on users as we’ve seen, and the two main dangers are:
SUCTION ENTRAPMENT Suction entrapment occurs when a swimmer is trapped by the suction forces created by the water flowing through the outlet drains at the bottom of the pool or low wall suctions (human skin is unfortunately able to form a perfect seal!). In some cases, swimmers have been trapped underwater until they drowned and in other cases, they have suffered serious injuries to various parts of their bodies including the bowel. The suction produced is very powerful.
HAIR ENTANGLEMENT When bathers swim too close to bottom drains or suction outlets of incorrect design with uncontrolled water flows, or place their heads underwater in a spa too close to incorrectly fitted, or non-present anti-vortex fittings, these water outlets create a vortex (a circular motion) and long hair can become entangled in the grilles at the outlets. It has also been noted that any fitting with these design defects at a specific outlet fitting can potentially cause this entanglement – main circulating and / or booster pumps. Examples of potential sources of suction entrapment / hair entanglement • Incorrect operation • Incorrect fittings • Poor design of drain outlets and covers • Insufficient number of drains • Creation of one line suction to main circulation or ancillary pumps by incorrect
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Broken grids are a potentially lethal problem
operation of critical valves • Vortex formed over fittings − anti-vortex fittings not fitted • All one-line suctions eliminated, and surface water draw-off overflow pipework valves locked open to prevent the creation of one-line suctions for example • All fittings are made secure so they cannot be removed • Velocities through outlets not adhering to recommended rates • Broken grids – a potentially lethal problem. It is therefore imperative that the pool operator is fully trained and aware of the potential dangers, and continually manages and risk assesses the operation of critical valves, line velocities and fittings, etc. Refurbishment or alteration of any pool or water-based facility should also always be risk assessed to ensure no additional risks are introduced in relation to suction entrapment and hair entanglement. It should be noted that facilities with balance tanks for deck-level systems do not normally produce these risks as the water flows by gravity to a tank before direct suction to the pump(s).
WHAT DO THE STANDARDS SAY? As pool operators, we must ensure that our inlets and outlets comply with BS EN 13451 which requires all swimming pool operators to ensure there are no risks and dangers from inlets and outlets in pools and spas. STA has created a list of items that should be checked and adhered to, in order to ensure compliance: • At least two outlets, minimum 2m apart
Suction entrapment can lead to life-changing injuries and worse
and at least 3m from side walls • Speed of water going through the gratings should not exceed 0.5m/second, and correctly sized as per PWTAG guidance • Inlet and outlet grille and cover apertures should not exceed 8mm • Outlets are designed so that it is impossible to block them completely. In addition, STA recommends that inspections should be undertaken routinely by professionally trained personnel (if necessary including with professional divers under HSE Diving Regulations). A visual inspection should be carried out daily to ensure no damage has occurred or grilles have become loose, and a closer inspection should be undertaken monthly. The hair entanglement test can be done in the form of a wig test, as per PWTAG’s Swimming Pool Water publication. Also, there are devices that can be installed to prevent suction entrapment, such as Vac-Alert. All inspections should be recorded and suitable procedures in place should any damage or missing items be identified. For further details please refer to the: • PWTAG Code of Practice Hair Entrapment Test Procedure • PWTAG Technical Note (TN66) ‘Suction Entrapment in Spa Pools’. or contact STA’s Technical team for details on all of our professional pool and spa plant qualifications via www.safetytrainingawards.co.uk STA 01922 645097 www.sta.co.uk
As pool operators, we must ensure that our inlets and outlets comply with BS EN 13451” www.swimmingpoolnews.co.uk 23/10/2024 08:02