Scuba Tech Tips: Prepping For Cold Water Diving


By Alec Peirce

We need to talk about something for with which I have a lot of experience.  I have been diving a very long time – 60 years as you know. I have dived all over the world and in many oceans, different environments, fast water, dirty water, good water, bad water, and some places where I shouldn’t have been. One particular area of diving experience for which I am very familiar with is cold water.  Having been born and raised in Ontario, Canada we have this thing called “winter” up here – I am sure you have read about it.

When I started diving in 1958, I was very young, and all the diving was in cold water. I didn’t do ice diving when I was that young, in fact for a number of years until some of the local club members got together and organized an ice dive.  From roughly 1970 to about 2000, that’s 30 years – I did a LOT of cold water diving and almost exclusively in the Great Lakes. On a good day in the Great Lakes temperatures might reach 60F degrees. In the spring the water is about 35F degrees – that is about 2 degrees Celsius, that’s cold.

Let me explain how we do Ice Diving.  We walk onto a frozen lake and find a spot that we believe may have something to look at under the ice like a wreck. We then cut a triangular hole in the ice – we cut it this way because it is easier to get out of the water with a triangular shape. The ice itself is obviously 32F degrees (0C), however, the water underneath is actually warmer.  When ice diving we have people, who come along called “tenders”. They are folks who are tending to the safety line attached to each diver. Tenders get very cold as the weather above the ice could be -5F, yet the divers are warm because they are in 35F degree (2C) water. 

The point is that I have done a lot of cold-water diving and on more than one occasion I have had my regulator freeze-up more than once.  Of course, it is unsafe unless you are careful, calm, and aware that you can lose air very quickly, which can be dangerous, but you can still safely get out of the water. What is worse – your diving is over for the day! If your regulator freezes up on a dive it is almost impossible to make another dive with that same regulator even if you warm it up. It really is a big nuisance since you had to drive to the dive site, lug heavy gear around and get into diving gear. Ice diving is a lot of work.

Paramount in most diver’s eye is how to keep gear functioning properly. We are going to talk about dry suits in another episode as well as some other equipment for cold water diving in the future. Today, however, I am going to talk about your regulator and how to keep it from being a problem on an Ice Dive. I need to point out that you actually don’t have to be under the ice for a regulator to freeze up. It can freeze in water 40F (4.5C) as well. For example, in the middle of summertime in the Great Lakes, the surface water temperature may be 60F to 65F degrees (15C to 18C), however, once you drop down below 40 to 50 feet you hit what’s called a “thermocline”. The water below the thermocline can be 40F to 42F degrees (4C to 6C). If the regulator freezes at 50 feet down, it is important to note that when a regulator freezes, it does not cut off the air supply it is in fact the opposite – it free flows as it is designed to do. 

So how do you prevent a regulator from freezing?

There are a number of things you can do including myths and misconceptions floating around.  Some misconceptions are that some regulators don’t freeze or old two hose regulators don’t freeze.  Sorry – but they can. Let’s look at this particular regulator, the Sherwood Blizzard, designed specifically for diving in extreme conditions including cold water. It does have some features that will reduce the likelihood of it freezing. Yes, that is helpful but they may still freeze. Some regulators have what is called an environmental kit. All first stages have holes in the first stage so that water pressure can exert pressure on the piston or diaphragm to get air pressure at the right level. Some regulators come with a special sealing first stage cap and some oil is in there so water doesn’t get inside the regulator. Again, people believe this is an “antifreeze kit” and the regulator won’t freeze up.

The water that goes inside holes in the first stage or second stage are not the problem, they have to be there. A regulator freezes because of the moisture in the air that you are breathing. There is a process called “adiabatic”, and that process is a physical process that explains that the temperature will decrease as the pressure decreases.  Remember what does the first stage in a regulator do? It takes pressure at 3000 psi and reduces it to ambient pressure which can be as low as 15 to 30 psi. That is a big drop and in that big pressure drop, based on the principle of adiabatic, the temperature of the air of the device drops considerably. The air that you are breathing is clean and very dry – it’s supposed to be that way – and the adiabatic temperature drops is great enough as you are breathing through the regulator, then the very small amount of moisture remaining in the tank air can freeze.  It transforms from “water vapor” to “ice crystals” and those ice crystals will settle on the valve so the next time it tries to close, it cannot close, so the air continues to flowing, as it flows it gets colder, more ice crystals develop on the valve and you end up with a sudden regulator free flow.  Nothing to do with the water temperature at all.

In fact, you can make your regulator freeze without putting it in water. If you on a lake with your tank all ready to go, the regulator is attached and checked, laying outside on the ice while waiting for your turn to ice dive, say 10 to 15 minutes. Then you go to that cold tank and turn on the air and breath in through the regulator, it could freeze up and free flow outside the water. It has little to do with the water you are diving in, it has to do with the temperature drop because of the pressure drop.  

Some important tips to avoid the regulator from freezing. First, get the driest tank air you can. When you go to a dive store look at their air quality certificate which should tell you how dry the air is. Secondly, make sure your regulator is dry. Put it on a tank and in a warm environment, and breathe through it for several minutes. The dry tank air will clean out your regulator and dry it completely before you go outside for the ice dive. Thirdly, if you are going on an ice dive or cold water dive, keep the regulator warm.  Fourth, keep the tank warm and the air in it warm. If the tank air is warm then the drop in temperature from the pressure drop takes little longer and you may not get a free flow.

Lastly, don’t breathe the regulator on the surface as the air temperature can be much colder than the water temperature.  If you start breathing above the surface, the adiabatic process will cause a temperature drop that can freeze up a regulator.  Make sure your first regulator breath is after your regulator is under water. Hope there is some helpful tips to think about for divers heading out for your first ice dive or cold water dive.