Simulation of Water Circulation Improves Safety of Swimming Pools.

LEBANON, N.H. -- 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

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 deaths. Now Ray Cronise, Co-Founder of Trilogy Pools, has come forward to state that the premise under which drains were included on the vast majority of pools that have been built is faulty. He concludes that the 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.

Cronise's ideas strike 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," Cronise said. He approaches the problem from a different direction, asking whether the drain is necessary and even questioning whether there is any advantage to having a drain in the first place.

With a technical background that includes both undergraduate and graduate degrees in chemistry, Cronise knew that advancements in the last several decades have made it possible to simulate the flow of fluids with a great deal of accuracy. Cronise and Dave Schowalter, a lead consulting engineer with Fluent, the largest developer of computational fluid dynamics (CFD) software, worked together to simulate the flow of water through computer models of swimming pools. The simulation involved placing contaminants in various areas of the pool and tracking the amount of time needed to remove them using the pool's circulation system both with and without drains.

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.