Question 2nd stage wet breathing issue (Scubapro G260)

[mattvish]

Hi everyone,

My second stage keeps breathing wet; I've tried everything I can think of. I hope someone here can give me a hint about what could be causing the issue and how to fix it.

I got a Mk25 with G260 for my sidemount rig around 9 months ago. The first couple of dives were no issue, and I was very happy with the regulators. However, from the second trip onward, I kept getting water into the second stage, first the left one and soon both. Normally, towards the end of a breath, I get quite a bit of water ingress.

I've checked the diaphragm, exhaust valve, cracking pressures, o-rings, and changed mouthpieces, but found nothing obvious and no improvement. I brought it to a local Subapro service center, and they checked and said it's from the mouthpiece. They put new cable ties, and it worked for a couple of dives, but the issue came back.

I've tried to determine where the leak is coming from, and it feels like it comes from the diaphragm. During the "vacuum test," it seems to hold to some point until the exhaust valve collapses. Sometimes it helps when I open the second stage and clean the diaphragm with fresh water; then it works for a bit until they leak again.

It's a very strange phenomenon. I know there are really only three reasons for a wet breathing regulator, with a fourth and fifth that are unlikely:

1. The diaphragm: It has a tear in it or is not properly seated.
2. The mouthpiece: It has a slice in it or is not the proper one for the reg.
3. The exhaust valve: There is dirt/debris/crud between the valve and the case. It is torn or has folded into the case.
4. A cracked case: But not likely.
5. Hosing missing o-ring or proper o-ring.

I can only imagine that there is an issue with the diaphragm seating, maybe a manufacturing defect? My next idea is to bring it back to the service center (even I don't really trust them) and tell them to replace the diaphragm; maybe that solves it.

I would appreciate it if anyone has any good ideas.

 

[davehicks]

If it really is the mouthpiece, try this. Put a couple of loops of electrical tape around the stem before putting on the rubber mouthpiece. This will make it just a bit more snug.

 

[Tom_Ivan]

Maybe completely eliminate the Mouthpiece by removing it entirely and going for a dive without one.

I'm pretty sure Vance Harlow has a test for wet breathing where you rotate the reg upside down and see what happens. Can't remember exactly what that tell you though. I'll try look it up.

 

[undrwater]

"vacuum test," it seems to hold to some point until the exhaust valve collapses.

There may be a clue here. I can't imagine why the exhaust valve should collapse.

 

[Jens Bölte]

Hello,

Detach the second from its hose. Do an underpressure (vacuum) test simply by inhaling through the mouthpiece sealing off the hose connection (your thumb will suffice). You can do the test with the mouthpiece attached and detached. You should not be able to inhale.
I am surprised to read that the exhaust diaphragm collapses in your underpressure test. I never get the exhale diaphragm to collapse in an underpressure test.
If the underpressure test fails when the mouthpiece is attached and detached

• Inspect the diaphragm holding it against some light. Punctures are easier to spot against light. Stretch the diaphragm a little bit while inspecting it.
• The exhaust diaphragm is hardly ever damaged. When folded in, it usually „floods“ the second stage. Put it back in place.
• Missing o-rings or a missing washer are more difficult to detect if you don‘t have the technical information. But I doubt that this is the cause given that the problem evolved over time and happens in both second stages.
• Inspect the body of the second stage for holes with a small torch.
• If the underpressure test fails when the mouthpiece is attached, inspect it for punctures by bending it. If no puncture is found, install an original mouthpiece if a non-ScubaPro mouthpiece was installed.

Best wishes Jens

 

[happy-diver]

Maybe completely eliminate the Mouthpiece by removing it entirely and going for a dive without one.

I'm sure if you go test out your invention first you won't be able to physically do it to suggest it again

 

[Tanks A Lot]

The R195 and G260 share the exact same body (11.331.021P) and diaphragm (11.331.012P). These parts are not used in any other ScubaPro second stage. They do have different diaphragm retaining rings, which is irrelevant to my main point below.

I have seen this exact same behavior you have on probably more than two dozens R195. The culprit was always the main diaphragm ever so slightly getting pinched below the diaphragm ring (11.331.104). Some of them did this after a month of usage, some after a year and nearly all never had this happening.

If you look careful at the diaphragm, it's "lower lip" is rather small, much smaller than say an old R190.

Additionally, the diaphragm is a tad smaller in diameter than the housing where it sits in. Again, compare that to an old R190 diaphragm, which usually sits right towards the edges of the R190 housing.

Now factor in ever so slight manufacturing differences, especially with regards to the diaphragm retainer and how that screws in. ScubaPro uses that little case pin (01.075.132) to stop the purge cover from loosening. Unfortunately that means that the purge cover is not always screwed in home enough.

If all three things come together, the small lip, the diaphragm being a tiny bit too small, and the purge cover not screwing in enough, the diaphragm will dislodge a tiny bit and start to leak.

To make things worse, unscrewing the purge cover will usually make the diaphragm pop back in place. I know this as I nearly got mental over this, before I decided to inspect the diaphragm from the exhaust port. Shining a small light into it revealed the subtly dislodged main diaphragm.

The solution is fairly simple. Remove the case pin (01.075.132) and do not use it again. Rather screw in your purge cover a bit tighter, to put enough pressure on the diaphragm. Obviously do not overdue it... I have not gotten a single unit back with the same problem after doing this. I have tried swapping diaphragms to no avail. I did replace one purge cover (11.331.036), which also fixed the issue, but was of course more expansive than just leaving the case pin out. It felt to me like it screwed in further than the leaky combination. The downside of leaving the case pin out is of course that the nice ScubaPro logo is not aligned anymore, but I guess that is not important to most people.

In the end I believe the diaphragm is poorly engineered. Too small at the lip and too narrow in general. Problems arise very rarely though.

Maybe this picture shows better why the yellow diaphragm dislodges easily when the cover is not screwed in far enough:

 

[mattvish]

The R195 and G260 share the exact same body (11.331.021P) and diaphragm (11.331.012P). These parts are not used in any other ScubaPro second stage.They do have different diaphragm retaining rings, which is irrelevant to my main point below.

I have seen this exact same behavior you have on probably more than two dozens R195. The culprit was always the main diaphragm ever so slightly getting pinched below the diaphragm ring (11.331.104). Some of them did this after a month of usage, some after a year and nearly all never had this happening.

If you look careful at the diaphragm it's "lower lip" is rather small, much smaller than say an old R190.
View attachment 818910

Additionally, the diaphragm is a tad smaller in diameter than the housing where it sits in. Again, compare that to an old R190 diaphragm, which usually sits right towards the edges of the R190 housing.

Now factor in ever so slight manufacturing differences, especially with regards to the diaphragm retainer and how that screws in. ScubaPro uses that little case pin (01.075.132) to stop the purge cover from loosening. Unfortunately that means that the purge cover is not always screwed in home enough.

If all three things come together, the small lip, the diaphragm being a tiny bit too small, and the purge cover not screwing in enough, the diaphragm will dislodge a tiny bit and start to leak.

To make things worse, unscrewing the purge cover will usually make the diaphragm pop back in place. I know this as I nearly got mental over this, before I decided to inspect the diaphragm from the exhaust port. Shining a small light into it revealed the subtly dislodged main diaphragm.

The solution is fairly simple. Remove the case pin (01.075.132) and do not use it again. Rather screw in your purge cover a bit tighter, to put enough pressure on the diaphragm. Obviously do not overdue it... I have not gotten a single unit back with the same problem after doing this. I have tried swapping diaphragms to no avail. I did replace one purge cover (11.331.036), which also fixed the issue, but was of course more expansive than just leaving the case pin out. It felt to me like it screwed in further than the leaky combination. The downside of leaving the case pin out is of course that the nice ScubaPro logo is not aligned anymore, but I guess that is not important to most people.

In the end I believe the diaphragm is poorly engineered. Too small at the lip and too narrow in general. Problems arise very rarely though.

Maybe this picture shows better why the yellow diaphragm dislodges easily when the cover is not screwed in far enough:
View attachment 818913

Thanks A lot! That was the answer I have been looking for, good to know that I'm not imagining the issue. It's a pity that Scubapro did not fix the issue of the R195 with the G260 iteration. I will try to to get the cover tighter and test it next chance

 

[johndiver999]

Wow good explanation. Also you don't want to do the vacuum test too hard, that might well be dislodging the diaphragm or the exhaust valve.

 

[rsingler]

This machined clearance, nicely explained by @Tanks A Lot, is exactly the same reason why Scubapro's environmental seals always leak, and why we see recurring reports of champagne bubbles from Apeks regs at the 2 year mark.
These soft components depend for their seal on a perfectly calibrated distance between the two sealing surfaces to provide compression. Alas, while the machined components may be consistent, lot-to-lot, the soft components are not...