Problems with Braided Regulator Hoses

While most of our subscribers are members of DAN, and therefore, receive their magazine, Alert Diver, we think it's important to call attention to a recent story (winter 2017 edition) that points out a potential problem with the lightweight, flexible hoses that have replaced the old, standard, rubber-covered regulator hoses. They are so flexible, they can be tied in knots!

DAN has reported a regulator failure that was caused by this type of hose becoming restricted in such a way that for the diver, it seemed as if he was out of air; however, the tank was not empty. The inside of the braided hose had become blocked with a polymorphic crystallization related to the molecular structure of the internal tube -- a phenomenon associated with cyclical heating and cooling.

It seems that the sun may heat up the hose, and when the tank valve is opened, the flow of depressurized air then cools it rapidly. This happens before every dive, causing tiny crystals to form and accumulate over time. As they grow, these crystals can either block the hose or migrate into the second-stage, resulting in a significant failure.

The incidence of failure is quite small. However, because this occurs internally, it is not visible to a diver looking at the hose, so the deteriorated internal surfaces go unnoticed. That means divers should periodically examine these hoses by squeezing them every inch or so along their length to assess whether they exhibit the same degree of flexibility. Any change in resistance would be a sign of an impending problem.

If you're diving in hot tropical climates, you need to know that DAN believes these hoses have a limited functional life, because the internal surfaces appear to be prone to this crystallization in hot weather. If you notice any gas-flow restriction, cease using your regulator.

To better understand the phenomenon, DAN wants more information. If you observe this degradation in your regular hose, please contact DAN, preferably with pictures showing the condition of the hose. research@dan.org