Free Flow Regulators in Cold Water


Version 2 – Oct 2007

Free Flow Regulators in Cold Water

Fresh water sites can often be close to freezing, even outside the obvious winter period. This√ā¬†often poses the threat of a free flow. Incidents resulting from free flows cannot be completely√ā¬†avoided but they can be reduced if a few basic guidelines and procedures are followed.

What can cause a free flow to occur?

When air flowing from a diving cylinder is subjected to dramatic reductions in pressure (a√ā¬†change from 230 bar to around 10 bar) by the regulator first stage, it loses a lot of heat. If the√ā¬†surrounding water temperature is cold (around 5oC or less) this will reduce the temperature√ā¬†still further. The very cold air caused by such temperature drops in each stage of the regulator√ā¬†can cause any water droplets within the mechanism to form ice crystals, which in turn can√ā¬†cause a free-flow.

Modern down-stream valves will freeze open rather than shut, but, if they freeze, a free-flow√ā¬†will always be the result. Divers are trained to manage free flow situations in basic dive√ā¬†training.


Diving in conditions that are cold can increase the likelihood of a regulator free flow. Being√ā¬†prepared and anticipating this event will increase your chances of dealing with the incident in√ā¬†a safe and controlled manner.

Use a cold water environmentally sealed regulator. The most important consideration√ā¬†will be to have the regulator serviced regularly specifically for cold water. Many of the√ā¬†top regulators meet the European standard (EN250) for cold water (defined as 4oC).

  • Familiarise yourself with the adjustments you may want to make at the dive site and√ā¬†follow proper cold water diving principles detailed below.
  • Try to ensure that your cylinder is kept free of moisture and has been filled√ā¬†with air containing as little moisture as possible.
  • Keep your cylinder out of the cold until you are ready to use it. (Don’t leave it√ā¬†in your car overnight.)
  • Blow away any entrapped water (or ice) that may be on your cylinder valve or√ā¬†regulator orifices, with a little air from your cylinder.
  • Take check-out breaths submerged in shallow water immediately before√ā¬†diving rather than in the air.
  • Avoid the cooling effect of fast air flows caused by using the purge button or√ā¬†breathing heavily, or filling delayed SMBs or lifting bags.
  • Do not permit any water to enter the 2nd stage before or during the dive.
  • Consider restricting yourself to no-stop diving, and to a depth from which you√ā¬†are certain you are able to make a free ascent.


  • Practice free flow regulator drills and the use of redundant air supplies for such√ā¬†instances. The use of a redundant air supply such as a pony bottle and regulator, or√ā¬†an additional first and second stage mounted onto a Y-valve should provide reliable√ā¬†source of additional breathing gas when a free flow occurs.
  • Ensure all alternate air source systems are in plain view and conspicuously marked√ā¬†allowing access at all times.
  • Discuss the in water procedures and techniques that should be used when dealing√ā¬†with this situation and clearly agree with your buddy on the action to take in each√ā¬†case.

In-water response to a free flowing regulator

When a regulator suddenly goes into free-flow it can be very startling as there is a sudden√ā¬†roar of bubbles and visibility is reduced. The main strategy is to:

  • Remain calm Stop – Think – Act
  • If you are confident in breathing from the free flowing regulator do so, but check and√ā¬†prepare alternate sources just in case.
  • If an alternate air supply is preferred and available switch to it. An alternate air source√ā¬†might constitute an √Ę‚ā¨ňúoctopus√Ę‚ā¨‚ĄĘ regulator or a fully redundant air supply, such as a pony√ā¬†cylinder and regulator.
  • Abort the dive and head for the surface in a controlled manner with your dive buddy
  • Once on the surface, establish positive buoyancy as soon as possible

Breathing from a Free Flow

Modern high-flow regulators which freeze open can produce extremely powerful free flows.√ā¬†Even very experienced divers may find it difficult to breathe effectively from a free flowing√ā¬†regulator in these circumstances. Practice breathing from a free flow regulator as indicated by√ā¬†your training organisation. Whichever method is adopted ensure that you do not seal your lips√ā¬†around the mouthpiece. You may use your tongue as a splash guard to prevent choking on√ā¬†water.

This technique takes practice to perfect and to feel comfortable with it, so take every√ā¬†opportunity to simulate it in safe conditions. Moderately powerful free flows can be simulated√ā¬†by pressing the purge button.

Do not assume that you or your dive buddy will always be able to breathe from a free flowing√ā¬†regulator √Ę‚ā¨‚Äú be prepared to switch to a normally operating source of breathing gas, or to offer√ā¬†your buddy an alternate air source, if required. Bear in mind the possibility of your alternate air√ā¬†source also free flowing in very cold water. The use of pony cylinders and regulators offer√ā¬†divers a fully redundant air source in these circumstances.

Using and alternate air source supplied by another diver

The most common alternate air source is the alternate second stage or √Ę‚ā¨Ňďoctopus,√Ę‚ā¨¬Ě normally√ā¬†secured in plain view in the triangular area between the chin and the corners of the rib cages.√ā¬†Whether the donor breathes from the primary or the secondary regulator depends upon the√ā¬†regulator configuration and other factors. Generally, it is desirable for the donor to retain the√ā¬†primary regulator and provide the alternate, but alternate inflator regulators and other√ā¬†configurations (such as redundant air supplies) have require the donor giving up the primary√ā¬†to the receiver and then switching to the alternate. The important point is that buddies know√ā¬†how each other√Ę‚ā¨‚ĄĘs systems work.

The receiver secures the alternate after sufficient time to adjust. The team establishes contact√ā¬†and then ascends face-to-face or side-by-side as appropriate for the configuration, with the√ā¬†face-to-face, grasping right fore arms the most common. During the ascent, divers control√ā¬†their buoyancy to maintain a normal ascent rate.

By implementing some of the suggestions above and by discussing possible reactions to a√ā¬†free flowing regulator with your buddy, you will reduce the likelihood of such an event√ā¬†occurring and improve your responses to the situation should it arise.


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