Main Drain Safety
Entrapment injuries in swimming pools steadily increased through the latter part of the last century, until they obtained national attention when the granddaughter of former U.S. Secretary of State James Baker drowned in the family hot tub by becoming trapped by the suction of a powerful main drain. This prompted the VGB act of 2007, named after Virginia Graeme Baker, as a result of the tireless efforts of her mother Nancy Baker, who lobbied congress for support for improved safety for pool and spa main drains.
New legislation mandated changes throughout the pool and spa industry. Main drain covers were designed and approved, and later redesigned and reapproved, to reduce the likelihood of being suctioned or stuck to the drain cover. All public pool and spas in the U.S. must use VGB compliant drain covers.
Design of drains was also affected, and new pools constructed, or existing public pools, must use a dual main drain system, a suction limiting system, a safety vacuum release system, or other system to disable the drain or pump when suction or vacuum pressure increases. These are described below.
Making Pool Main Drains Safe
VGB COMPLIANT DRAIN COVERS: Flat grates are out, raised anti-vortex drain covers are in. If your pool was built before 2007, your drain covers may be unsafe. Replacing with a drain cover that meets the ASME/ANSI A112.19.8 performance standard is recommended. However, of equal importance to the type of cover, is to be certain that the drain cover is firmly attached with both screws at all times.
DUAL MAIN DRAINS: Constructed of two main drain pots, connected to each other by piping and a Tee fitting. The idea is that the two drains are far enough apart that one person could not block both drains at the same time, and if one drain is blocked, suction quickly shifts to the other drain.
SAFETY VACUUM RELEASE SYSTEM: These devices connect to the pool pump wiring and plumbing. Sensors in the plumbing before the pump will detect if vacuum pressure increases beyond a set minimum, and when so, the controller shuts off power to the pump, to ‘release’ a blockage.
SUCTION-LIMITING VENT SYSTEM: This is when additional pipes are plumbed into the main drain pipe, and these pipes are vented to a height above water level. When engineered properly, a vent pipe can be used as a vacuum breaking system. When vacuum pressure reaches a certain threshold, the water from the vent pipe will be sucked into the pump, followed by a large volume of air, which will break the vacuum suction. Vent systems should be designed by a qualified engineer who can do the calculations necessary.
GRAVITY DRAINAGE SYSTEM: In this type of main drain set-up, the main drains are gravity fed into a collection tank that is connected to the pool pump. This arrangement produces suction only on the tank, and not on the drains, which drain downhill to the tank, located at a point lower than the main drains.
Residential Pool Main Drain Safety
- Replace flat drain grates or anti-vortex covers with VGB approved drain covers.
- Dive regularly to inspect drain covers; to be sure they are firmly attached.
- Teach the children of the dangers of main drain entrapment.
- Never use the pool without main drain covers safely in place.
- For pools with separate main drains, on a dedicated pipe:
- Never operate the pump with on main drain only, when swimmers are in the pool.
- Consider installing dual main drains the next time the pool is resurfaced.
A ‘separate main drain line’ is one that is not connected into the skimmer, which allows a certain element of safety against suction entrapment. If you have a separate main drain line (pipe) that runs all the way back to the pump, with a separate valve to control the main drain suction, this can be less safe, as it is connected directly to the pump suction.
Since the VGB act became law, there have been 39 entrapment injuries and 2 deaths reported from the period of 2008-2012. Injuries included bruises, broken hands or feet, and disembowelment or intestinal prolapse.
Entrapment is not always caused by extreme suction; many entrapments occur when swimmers get their hands, feet, hair or clothing caught in the drain cover or the drain pipe, and cannot escape in time.