\ARTICLE FROM SAFETY MATTERS NOVEMBER 2007
teach child aquatic safety, suction outlet entrapment avoidance to be exact. It
has come to my attention, (we) as an industry have created a dangerous situation
by demanding "dual drains" in new pools & spas. We now require dual drains and
anti-vortex covers in most States, when we should be requiring anti-entrapment
type suction outlet covers. Perhaps I can help make this clear by explaining the
difference between the two items. This could be a matter of a safe dual
drain system or a deadly dual drain system.
In the early 1970's, due to the advent of closed impellers and self priming pool/spa pumps came more powerful suction outlets and main drains. To prevent air from being entrained into the main drain via a vortex, anti-vortex main drain covers were developed. Not so much to protect children but to protect pump shaft seals and motors. Safety was not the issue as suction entrapment was not "in the news" at that time. One of the criteria of the anti-vortex cover was "a small open surface area", perhaps 10 square inches or less. These covers did indeed protect pump motors and the related seals, but not children. The turbulent area around the small open surface created a high velocity that could pull in hair or bathing suit ties, jewelry, etc., and in some cases harbored a finger entrapment potential.
Then, in the late 1970's we have child injuries and worse incidents began making the news. Studies were being done to use dual drain technologies to prevent child entrapment. These tests were done mostly on 12" X 12" main drains. The individual could "roll off" the 96 square inch open surface area and release himself. Remember, we are dealing with open surface area, not overall area. Open surface area on some 12" X 12" grates measure 96 square inches and the overall area of: 144 square inches. More testing should have been done with smaller sumps.
Now in 2007 we are recommending hydraulically balanced dual drains separated by a minimum of 3 feet. This may not be as safe as it seems. It is important that we remember the "small open surface area" of some covers. For example; we have a Code compliant dual drain system, we also have two ANSI/ASME A112.19.8 Standard certified Anti-Vortex drain covers with a small open surface area of approximately 8 inches. What if one drain cover becomes missing or dislodged? That open main drain pipe or sump can now have a force that could prevent a Child's escape. In other words, "he is trapped" to the forces from the pump suction under him and the weight of the water above him. The opposing drain cover (still intact) allows the pump to maintain a full head and hold the child to the unprotected suction outlet. This is a bad scenario.
So to recap: 1970 main drain cover, 1980 anti-vortex cover, 2000 anti-entrapment cover and now 2007 anti-entrapment type suction outlet cover. As we build more and more dual drain systems we need to understand the hydraulics involved. It would be far more beneficial to install large open surface area "Anti-Entrapment type suction outlet" covers to minimize the related suction hazards as well as allowing the pumps to operate with more fluid volume at a lower velocity. The connecting pipe between the dual drain sumps should be 2.5 inches in diameter or larger, not to exceed 6 feet in separation to avoid high hold down forces.
Bottom line is that it boils down to child safety. We need to focus on protecting children and understand how systems and products relate to each other and not just blindly install them without understanding the reasoning behind their development or effects after installation. We require education to be effective in our safety related efforts.
If we can assist your department in an educational venue please call:
Article Provided By,
drainsafe™ : The Solution
A Swimming Pool Suction Safety Corporation
Aquatic Professionals: (561) 433-2580 or 1-800-513-4372
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