Is a Vortex Visible on the Surface of your Pool?

Outlet grilles located on the pool floor are often fascinating  features to children when they first learn to swim underwater, particularly when the water suction is strong enough to be felt. Although entertaining, if the strength of suction becomes too high and no fail safe mechanisms have been installed in the outlets then this can provide a significant, and sometimes fatal, hazard.


In the USA between 2008 and 2012 thirty nine victims of circulation entrapment were recorded, including two fatalities, with 74% of incidents involving children under the age of 16. Official HSE Standards state that water flow should not exceed 0.5m/sec, however this can be a challenge to calculate with no experience.

Vortex Pool Surface
Example of a vortex identified in a recent CSD condition survey caused by high suction rates viewed from below the surface of the pool

An easy to spot indication of a high suction rate that must be remedied immediately is the presence of a vortex, picture shown above, on the surface of your pool.


Guidelines for new pools state that there should be a minimum of two suction outlets per pump, at least two meters apart, in addition to cut off mechanisms within the pump system to ensure entrapment does not occur. However, in existing pools installing new pipes and plumbing is extremely costly and is often not feasible.


Anti Vortex Grilles
Stainless steel and HDPE antivortex grilles

Anti-vortex grilles can be installed instead as a low cost and effective alternative, with little or no disruption to the day to day running of your pool. These are raised grilles, shown above, that allow water to pass both through the face of the grille as well as the perimeter between the grille and pool floor. This design means that it is less likely for all openings to be covered simultaneously, greatly reducing the risk of entrapment.


The presence of a spiraling vortex of water can also pose a risk due to entrapment of long hair. If long hair is pulled through a grille that is creating a vortex then it is more likely to wrap around itself and tangle, therefore trapping a swimmers head underwater and potentially leading to drowning. CSD can conduct hair entrapment tests to ensure that this is not a potential hazard.


We keep a variety of anti-vortex grilles in stock, that can quickly be installed underwater by our divers, to ensure that we can rectify any identified entrapment hazards as quickly as possible.