Stop Swimming Pool Suction Entrapment Accidents

Needless drain can lead to swimming pool drowning accidents

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Since the 1980's there have been at least 147 incidents documented of suction entrapment in swimming pools, including 36 deaths. Suction entrapment occurs when a swimmer, usually a small child, is trapped by the suction forces created by the water rushing out of the drain at the bottom of the pool. In some cases swimmers have been trapped underwater until they drowned and in others they have suffered serious injuries to various parts of their bodies.

The swimming pool industry has made serious progress in improving the safety of drains and this has reduced but not eliminated some of the injuries and drowning. The premise under which drains were included on the vast majority of pools that have been built is faulty. Deaths and injuries caused by suction entrapment can be completely eliminated, without any negative effects, by sealing the drains in existing pools and not building drains in new pools.

This idea strikes at the heart of one of the main principles of swimming pool design. The pool industry has long used drains because of the belief that they are required in order to provide circulation throughout the pool so that contamination will not remain in stagnant areas but will rather quickly pass through the filter where it can be removed. Is the drain necessary and is there any advantage to having a drain in the first place.

Computational fluid dynamics was used to simulate the flow of water through computer models of swimming pools.

Contaminants were "placed" in various areas of the pool and the amount of time needed to remove them using the pool's circulation system both with and without drains was tracked.

The simulation showed that the contaminant concentration was actually higher at most of the monitoring points in the pool with a drain during the first 1000 seconds of the simulation.

But at about the 1000 second point, the contamination in the pool with a drain dropped to the level of the pool without a drain and the two pools showed essentially identical results from that point on. The simulation showed that inlets and skimmers alone are sufficient to clear contamination to levels of about 0.0015 within about 1000 seconds. After that point, the circulation system continues to reduce the level of contamination to about 0.001 after 6000 seconds.

The circulation of water is something that is nearly impossible to see and very difficult to measure so in many cases pool designers have been using drains simply because the pools that were built in the past have used them. This simulation clearly shows that drains not only are not necessary, but they do not improve the circulation in a pool or enable its ability to clear contamination. The number of injuries and deaths caused by drains in pools is not large compared with other hazards, yet future deaths and injuries can be prevented at no additional cost simply by getting rid of the drains.


Updated by Dr. John Mullen on February 29, 2016