Mouthpiece tears and silicone mouthpieces

[John C. Ratliff]

I was diving this regulator as a backup, with a neck strap. I took it off and examined it and found that the neck strap had caused it to tear badly. The USD second stage was a backup on my Mossback Mk III double hose regulator, and the neck strap was an old one meant for a Sportsways regulator. The neck strap was made of neoprene, and had a cutout for the mouthpiece. I put the mouthpiece through the hole, which I had enlanged so that it was not too tight.

Originally I thought that this was a problem of the neck strap, but a couple of days ago I took out my Sherwood Magnum Blizzard regulator to look at the O-ring in the first stage. This was in response to Luis' discussion about O-rings in the thread about Need a Rebuild Kit for AL Deepstar I First Stage. That Sherwood regulator's second stage also had a clear silicone mouthpiece, and upon examination it has cuts all the way through the mouthpiece that could leak water in certain positions. This is one of the factors which apparently led Chrissy Rouse to abort his decompression and was perhaps the final straw in a double fatality involving him and his father, as detailed in Bernie Chowdhury's book The Last Dive, Perennial, 2000, page 275 (paperback edition).

Chrissy now switched to the scuba bottle that his father had clipped to him after they escaped the wreck. But instead of breathing air, only water came through the mouthpiece. Postdive analysis revealed a torn mouthpiece that would have allowed water to enter.

My question is whether any of you have had this experience with silicone mouthpieces, especially older ones. Also, if anyone knows about the composition of silicone, and whether it is more prone to this kind of tearing, I would appreciate knowing about this. My experience is that older neoprene mouthpieces will deteriorate, crack around the edges, but I haven't seen this kind of tearing at all in them. Only the clear silicone ones (two in my experience now, but I only have two of them for a 100% failure rate--small sample size) have torn.

SeaRat

 

[dumpsterDiver]

I think silicon will tear easily when it begins to rip. But they do last a long time in my experience.

 

[Ed Palma]

I've seen one mouthpiece go on a set of rental gear. Well, one of the bite-tabs ripped off, so it wasn't as leaky as yours. Examination of the mouthpiece revealed it to be pretty beat up, so I guess with a brief inspection beforehand, most suspect mouthpieces can be caught before anything serious happens.

 

[John C. Ratliff]

I just found two other of my regulators which have this mouthpiece, and they are still okay. So the failure rate for me is down to 50%.

John

 

[Couv]

John,

It's hard to tell from the picture, but it appears that mouthpiece is one size too small for the regulator you have it on. Also, is looks like the flange might be part of the problem. Is it in any way cutting into the mouthpiece?

couv

 

[dumpsterDiver]

The flange on some metal regs has been an issue for me also. i have used a couple of wraps of electrical tape over the sharp edge and then installed the mouthpiece.

 

[Zung]

Some of my mouthpieces have turned 20, and I never have a problem except with my #2 son's, but he chews them, so I guess it doesn't count.

All of them are original SP's, mostly black.

Btw and in case of emergency, tearing off the rest of the mouthpiece and breathing off the orifice is OK. That's how I test the cracking pressure: with a piping in the corner of my mouth, it's a lot easier than with the mouthpiece on.

 

[John C. Ratliff]

couv,

I never knew that there were different sizes for these mouthpieces. Thanks, I'll check into that.

Zung,

Good observation. There are a number of things about that accident. For those who haven't, it makes an interesting read. The purge button comes to my mind as another alternative. But that require a cool head, and I think that was missing after all the other problems that this diver had. This was simply the "last straw" in a significant number of factors which went wrong with that dive.

SeaRat

 

[Couv]

If you have the opposite problem, The Master Awap suggest a big ass o-ring to assist in sealing. An o-ring at the flange to mouthpiece interface might have prevented the tearing you experienced.

 

[John C. Ratliff]

I don't think the metal tube is the problem, as my problem with the Sherwood Magnum Blizzard is with a plastic regulator. I'll look again tonight, but it seems to originate on the outside, not the inside of the mouthpiece for the tear. It's like the shear force from being bent is the problem, rather than the seal around the plastic/metal interface between the mouthpiece and the regulator tube.

SeaRat