Most pool owners and operators have heard the term VGB compliant as it relates to main drains in swimming pools, and may have heard of the Virginia Graeme Baker Pool and Spa Safety Act that was brought into legislation in the United States.
As a member of her community swim and diving team, Virginia Graeme Baker was a strong swimmer who could swim unassisted at only 3 years old. Despite this, Virginia (called Graeme by her family) died in a spa (hot tub) after becoming trapped on the single main drain fitting of the spa, even with the frantic efforts of her mother, Nancy Baker to release her from the drain. Eventually, two men were able to release Graeme from the drain, but exerted so much force that the main drain fitting was actually broken in the process. At the very young age of 7 years, Virginia Graeme Baker died from drowning as a result of becoming entrapped on the main drain fitting of the spa.
MAIN DRAINS & THE RISKS
The danger of a single main drain in a pool or spa cannot be overstated; when a single main drain is covered and is the sole source of suction for a pump, a tremendous hold-down force is exerted on the person covering the main drain fitting. For a typical residential pool or spa with an 8” round drain, the hold-down force can be in the order of 739 pounds! Even the strongest person would be unable to overcome this kind of force. The larger the surface area of the drain the greater the force, even if the same pump is used. For a 9”x9” main drain, the force will be about 1191 pounds, and for a 12” x 12” main drain the force will be a whopping 2117 pounds! This is approximately the same weight as a skidof bricks! But becoming entrapped by the suction is only one of the dangers of an improper drain installation. People can also become eviscerated if they sit on an improper drain, or become entangled (hair and jewelry) if the velocity of water through the drain is too high, or the drain openings are improperly designed.
Following Graeme’s death, Nancy Baker worked tirelessly as an advocate for pool safety and through the political clout of her father-in-law, former Secretary of State, James Baker III, and in association with Safe Kids Worldwide, lobbies to congress to bring into law the mandatory use of anti-entrapment drain covers and other safety devices and methods.
Use VGB Compliant Main Drain Covers
Perhaps the most important change was the nature of the drain cover itself. Main drain covers are now required to be VGB compliant, meaning that they have a shape and openings that have been designed to dramatically decrease the likelihood of a person becoming entrapped. The drains are also sized for different flow rates so that the velocity of water moving through the surface of the grate does not exceed 1.5 feet per second. This low velocity decreases the likelihood that things like hair will be drawn into the grate creating an entanglement problem.
Use Multiple Main Drains
Another important safety measure in pools and spas is to never have a single main drain. In Canada, it is law that every public pool and spa have at least two main drains, and that these be spaced apart from each other by at least four feet (1.2m). If one drain fitting is blocked, the water has another path to go though (the other drain fitting) so that an ‘absolute’ vacuum cannot be achieved.
Use a Safety Vacuum Release System
Finally, another measure to improve main drain safety is the use of Safety Vacuum Release Systems (SVRS). These devices are installed on the suction side of the pump(s) and are designed to eliminate the suction force of the pump. There are generally two types (mechanical and electrical) which are designed to sense excessive suction and act to relieve this suction. Electrical units work by shutting of the pump, and mechanical systems work by allowing air to enter the pump so that it loses suction.
Swimming pools and spas provide a tremendous amount of fun, leisure, exercise and therapeutic benefits to families, the public and patients. But we have to always remember that pools are really machines designed for our aquatic needs, and like all machines, pools have inherent dangers that have to be managed. For decades, we drove cars without the benefit of seatbelts, airbags and so many other safety features. At one time, we didn’t even have windshield wipers! Thanks to the efforts of Mrs. Baker after her loss of Graeme, properly designed pools and spas are now safer than they have ever been.
Click here for more information on Virginia Graeme Baker, what you can do to prevent entrapment and other tragedies or to read the Pool and Spa Safety Act.