One-Way Valves

By Chris Gabel, Ocean Eye, INC.

Whether they’re on a helmet, a surface control system or hose, one-way valves are one of the most critical components in your system. If you didn’t get a chance, take a look at an old Myth Busters episode segment on YouTube ( to see just how important it is. I use this segment as a training evolution at my company. If that doesn’t make the point to a new diver or tender, nothing will.

If you look at Kirby Morgan, for instance, you are to test the one-way valve every diving day. On their daily check list, it states, “orally check the one-way valve. With the steady flow valve open, orally blow air through the one-way valve. Air should pass freely. Suck back on the umbilical adapter, and no air should pass back through the one-way valve and umbilical adapter. If air can be drawn back through the one-way valve, the one-way valve will require overhaul or replacement.”

You probably know all of this already, right? It’s drilled in to everyone at dive school.

Since we inspect and repair hundreds of helmets each year, we are bound to see some odd problems. One example we’ve encountered in regard to one-way valves found on helmets involves a bit of moisture and the weather. The situation involved a helmet with a mystery problem. When the hat is out in the field, the one-way valve was failing in the morning daily check. When the client would bring the helmet in, everything worked as designed. Go figure…The helmet would return to the job site and within a day or so, it would fail again.

The helmet was returned a second time and we opened up the oneway valve, this time water poured out. It turned out that the breathing air compressor didn’t have a moisture separator installed, and the client would put the helmet in the trunk of his car at the end of the diving day, which was parked outside in sub-freezing weather. The water would freeze in the valve and the valve would fail (either it wouldn’t shut when tested or would freeze closed.) So water did what water does. If you’re finding the same issue, check the valve for water intrusion.

Along with the daily test, regular maintenance is important. Make sure that any o-rings that may be installed are checked and/or changed at regular intervals. You will want to visually check that the valves are cleaned and maintained to the standard that the manufacturer outlines in their documentation. Confirm that you document any maintenance so that the next person knows there was something done to the helmet. I know it’s no one’s favorite task, but it will save a lot of trouble in the long run with your audit or (hopefully this never happens) a dive accident.

My motto with these kinds of components is, if in doubt, replace it. They are relatively inexpensive and it’s a type of insurance that breathing gas is not going to end up flowing in the wrong direction. It seems obvious, but we all get complacent with components that we check day in/day out and have never seen fail, until they do.

As always, dive safe.

Email your commercial diving equipment maintenance or repair questions to Chris at,