Think Twice Before Putting Your Gear in Rinse Tanks

Recreational divers typically rinse their equipment in "communal" tanks filled with fresh water after completing dives. Studies show these tanks are contaminated with bacteria, but the types of bacteria haven't been studied, nor have many studies addressed the possibility that communal rinse tanks may harbor pathogens and transmit disease. But it's proven that they do. Case in point: 14 divers at Fiji's Vitu Levu Island were diagnosed with conjunctivitis, which was traced to the eye infection of a divemaster who placed his mask in the communal tank (see our September 2008 story "Transferred by the Rinse Tank" for the story).

Michael R. Miller, a professor of biochemistry at West Virginia University, did an informal study at a Bonaire dive shop to investigate the extent to which bacteria was introduced into communal rinse tanks (see the results in our June 2009 article "Bacterial Contamination in Rinse Tanks"). Now, Miller and other West Virginia University researchers have made a more formal study, recently published in the journal Underwater and Hyperbaric Medicine, by testing bacteria in water samples taken from equipment and mask rinse tanks, as well as from ocean water.

During a dive trip at Belize's Ambergris Caye, they collected water samples for five days from these sources: their dive shop's hose used to fill a communal equipment rinse tank; the rinse tank itself; buckets on boats where masks were rinsed or stored; several dive sites at various depth; and ocean water at the dive shop's dock. In total, 30 samples were collected in sterile tubes and placed in a refrigerator. Back in the U.S., samples were separated and studied.

No bacteria were found in water samples from the hose used to fill the rinse tank. All samples from the equipment and mask rinse tanks contained levels of bacteria, the former containing the most diverse types. The extent to which bacteria were present in ocean water during various dives and by the dive shop dock varied greatly from low to high levels, but there was no apparent correlation with day or depth of diving.

Some of the bacteria were likely introduced by ocean water on divers' equipment, and some others may well have originated from the divers themselves. Although no bacteria in any of the samples could be considered overt human pathogens, two types of bacteria collected from open water are typically linked to water contamination, and could pose health problems to some people. Another type of seawater bacteria collected has been reported to infect wounds, and is resistant to many drugs.

From those results, the researchers show that due to the significant bacterial loads found in the communal rinse tanks. diseases could spread via the masks, regulators and other gear lying in them. To minimize the risk of infection, divers should rinse at least their masks and regulators in clean water rather than communal tanks. It's also advisable to spray or wipe masks and mouthpieces with a disinfectant, such as 70% ethanol, and give them time to dry before diving. "Identification of Bacteria in Scuba Divers' Rinse Tanks," by Brian Washburn, Andrew Levin, Kristen Hennessy and Michael Miller; Underwater and Hyperbaric Medicine, Vol. 37, No. 4, pages 233-240.