Second stage exhaust check valve failed open, flooding the reg when breathing

[serpentara]

I did a deco dive yesterday, and much to my surprise/chagrin when I switched to my deco gas at 20 feet, my first breath was actually a mouth full of water! I checked to make sure the tank valve was all the way open and the reg was purged and I tried again. Same result. I took a breath, and instead got a mouth full of water.

My ~50 min deco dive using air and 80% ended up being a 99 min dive on air alone. Thank god for proper gas planning! Still scared the hell out of me.

When I got home I took the reg apart and discovered that the one way check valve that covers the exhaust port on the second stage had folded under itself. Normally this only lets air out the vents on the bottom of the regulator when you exhale, and stops water from flowing in when you inhale, creating a vacuum, which pulls the large membrane on the back of the reg triggering a release of gas from the first stage. In my case, because this check valve was open all I got was a mouth full of water that entered in through the vent and through the exhaust port. My only theory is that the valve folded up when I did my giant stride in. Since the deco regulator is vent down, water rushed in unrestricted, rolling up the check valve.

My question is, any way to fix or even test this at depth? I am diving an OC setup so I could in theory take a drag at my 20 ft bubble check to see that everything is functioning, but what would a re-breather person do? They shouldn't exactly go off the loop at the bubble check.

Is there any way to fix this at depth? Flow the regulator at an angle somehow?

 

[uwxplorer]

Interesting question! And glad you had plenty of back gas for it not to be a serious situation...

You can in principle breath off a reg that has lost its mouthpiece, or breathing wet, free-flowing, etc, by letting it free-flow and gulp some gas putting your mouth above the gas path.
Obviously, that is not a tenable situation if you have to do significant deco with that gas.

On a rebreather, your best bet would be your buddy's BO. That's assuming he/she doesn't need it. And that you have a buddy!

If you've got a light and good short distance vision to confirm that the membrane is folded, your pinky might be all you need to put it back in place... Or the pencil you carry with your slate?

Some divers use regs with quick disconnect. In this case, having a spare in your pocket might be a solution.

I am interested to hear what others may suggest.

 

[DeepSeaExplorer]

There is a second pre-dive test to make sure a reg is working properly that is often skipped. After connecting the reg to the tank, and before opening the valve, attempt to breathe on the reg. You should get no air and feel and hear the exhaust valve give a little. This means the valve is properly sealing. So in addition to making sure the reg delivers air/gas when it's supposed to, there's also a second test to make sure it's not going to deliver water.

The exhaust valve can normally just be flipped back into position, but if it's worn or won't seal, it needs to be replaced.

 

[Agility]

some regs (e.g. the Apeks series) can be opened without any tools under water (though putting them together again with thick gloves might be difficult)

 

[The Chairman]

First, hit the purge hard. This will straighten out many issues with folded flap valves. Check it. If it's still wacky, then shake the first stage violently side to side. You can even hit the purge at the same time. Recheck. If you're still inhaling water, switch regs, take the first stage cover off and check things out. I remember a time at Peacock Springs Cave system. We surfaced in Sistine which has tons of duck weed. As I am descending back into the cave system, I was sucking water on one reg, so I switched to the other only to find the same problem. I breathed softly and took the first reg apart, cleared out all the duck weed, reassembled it and switched to that reg. I did the same on the other reg and it worked fine too. It should be noted that I was swimming the whole time. I think that disassembling a reg like this should be a part of any cave class.

 

[tbone1004]

Like Pete says, a violent exhale will usually blow the exhaust valve back open. Apeks XTX are nice because you can pop the exhaust T off without tools. Otherwise you can try to get your finger in there, but usually if you put your mouth or finger over the mouthpiece to block it off and then purge it will usually pop open. Not sure what tools you carry under water for dives like that, but you could start carrying an o-ring pick or even a stiff piece of shield 10 gauge wire would work. The better thing to do is what was said above and do positive and negative pressure checks at the surface. You can do it with the din caps on which is what I usually do or when they get on the tank before you pressurize, but inhale exhale on each second stage to make sure it is holding vacuum, takes 3 seconds per stage, but it would have saved you an hour in the water.

Ultimate in excessive is to put QD's on your hoses and carry a spare 2nd stage, this is sort of tongue in cheek, but it is what the UTD Z-system uses for "bailout" and would allow you to pop a spare 2nd stage in. For this, highly not recommended due to pure O2 use, and is expensive.

Basically, do a negative pressure check on your system before you go diving, yoke valves can do it with the dust cap ball thing in there, and din obviously seals against the cap, so do the proper checks and you'll be fine.

 

[John C. Ratliff]

One other quick thought--you can still breath off this malfunctioning regulator second stage, but not by inhalation. Inhalation creates negative pressure, which brings in the water. But if you look up and use the purge valve, you can breath off the second stage. It is a manual process whereby you need to hit the purge valve with each breath. Looking up on most single hose second stages puts the exhaust valve at the lowest point, and then you simply have a pool of water in the bottom of the regulator. But with the exhaust at the lowest point, you can get the gas out of the regulator with the purge valve.

SeaRat

 

[tursiops]

Avoid giant strides, or at least protect your regs when entering.
Breathe -- or at least inspect -- all your egs at the surface before descent.
The cover-the-mouthpiece-purge-and-shake usually fixes the problem. Now that you know what the problem is, it is easy to see U/W and probably easy to stick something in there and fix it. Just be careful not to blindly poke a sharp-tip knife in...you don't want a hole in that flapper!

 

[Dr. Lecter]

One thing to consider is a system like the Atomic M1 cave ring and exhaust tee: I can strip my second stages down very easily underwater to diagnose and solve problems like this (and for good rinsing/soaking) because of them. I suspect you can get the exhaust tee off most regs, though, and doing so here should have solved your problem.

 

[tursiops]

I suspect you can get the exhaust tee off most regs, though, and doing so here should have solved your problem.

It would now that he knows what the problem was....