Leaking DSV

[SurfLung]

Leaking DSV/Wet Intake Hose

- I have two DSVs that I was servicing lately. I was replacing the O-Rings in both of them. One of these originally came WITH Wagon Wheels and the other did NOT come with wagon wheels. The one that didn't come with wagon wheels has always fit the wagon wheels loosely. So this time, after replacing the O-Rings, I also wrapped one layer of electrical tape around the outside of the wagon wheels and that snugged up the fit perfectly.
- The first DSV that came WITH wagon wheels... I never removed the wagon wheels before and they didn't feel loose, so after replacing the O-rings in the mouthpiece, I left them alone and just put the hoses back on.
- Well after testing everything to be OKAY in the pool, I decided to switch these mouthpieces and regulators. So, I took the hoses off. And the one that had original wagon wheels had a soaking wet intake hose. In contrast the one with the electrical tape wagon wheels had a bone dry intake hose.
- So, I put the hoses back on the wet one and did a suck test... Sure enough the intake hose was leaking. So I replaced the hose clamps and did the suck test again. Still leaking. the hoses are brand new so it wasn't a leaking hose... Must be a wagon wheel valve. So now FINALLY I took the wagon wheels out of this DSV and look what I found...

- It's a special wagon wheel with an O-ring around the middle. I'm thinking the O-ring has far less sealing area than an original wagon wheel. So, I took off the O-ring and now the wagon wheel fit loosely like the other DSV. So, I put one layer of electrical tape around it and that snugged it up nice. Put it all back together and tested again at the pool. Now the intake hose is bone dry like the other DSV.
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- Final Thoughts ... Until now, I didn't really learn how to use the DSV to keep your mouthpiece dry. I was using it primarily to keep from free flowing at the surface. Here's what I think is the correct process:
1. Turn the mouthpiece DOWN (closed) before removing it from your mouth. This seals dry the large internal chamber of the mouthpiece.
2. Put the mouthpiece back in your mouth in the down position and (before turning it back up) blow gently to clear the water from the small outer section of the mouthpiece. You can feel the water squirting out of it under your lower lip.
3. Now turn the mouthpiece up and there will be no more water to clear. This comes naturally after a little practice.
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P.S. How do you like the white hosed DAAM above. I got those hoses from Rob at Scuba Museum!

[2THDIVR]

All my DSV's came with the wagon wheels with O-rings.
Pretty sure that's how they were designed.

Like the white hoses.

Info in this thread https://vintagedoublehose.com/forum/vie ... =47&t=8096

https://vintagedoublehose.com/forum/dow ... hp?id=2350

[luis]

Hi Eben,

The procedure you described here is correct.

1. Turn the mouthpiece DOWN (closed) before removing it from your mouth. This seals dry the large internal chamber of the mouthpiece.
2. Put the mouthpiece back in your mouth in the down position and (before turning it back up) blow gently to clear the water from the small outer section of the mouthpiece. You can feel the water squirting out of it under your lower lip.
3. Now turn the mouthpiece up and there will be no more water to clear. This comes naturally after a little practice.

The O-ring should actually provide a much tighter water seal than any plastic to tape contact, but if it is working for you, that is OK. The width or area of a seal is not really as important as having a continuous sealing border. There is a reason why O-rings are one of the most used and most reliable sealing methods.

The original wagon wheel were used inside a flexible rubber mouthpiece and a clamp was used to create a tight sealing line between the rubber mouthpiece and the wagon wheels.

With the hard plastic DSV tube, there is no way to create a tight sealing ring between the plastic tube and the plastic wagon wheels. Therefore, I had to add the O-ring to create a seal.

There is a catch to this. The wagon wheel drawing was modified to add the O-ring groove. The new wagon wheels will work on either the DSV or the vintage style rubber mouthpiece. But, the inside surface of the groove in some of the wagon wheels did not come out to be as a smooth surface as specified. Even with this situation I have found that replacing the wagon wheel O-ring work just fine.

There is always some tolerance (not all molded items are exactly the same) and I have occasionally used a slightly fatter (metric) O-ring.


BTW, I have found most leaks in the one way valves to be a bit intermittent and they seem to occur from the valve not always seating perfectly. Sometimes it can be just from sand or other contaminants, but that can now be avoided by closing the DSV and keeping the hose loop dry.


I do not recommend removing the O-ring seal and replacing it with tape, etc. YMMV

[2THDIVR]

Luis do you know what size the Orings are in the DSV?

Thanks
Scott

[luis]

I will post a diagram with all the O-ring sizes in a couple of days. I may have a chance to post it tomorrow night.

Thanks

[2THDIVR]

Thanks

[luis]

Here is a diagram showing the components of the DSV, including the three O-rings.

You will notice that I am showing the preferred O-ring and at least one option to account for possible tolerances on the clearance and fit.


Let start with the wagon wheel valve O-ring (Item # 6 in the diagram):

The design nominal O-ring is an SAE -027 (in either 70 or 50 durometer).

If there is a loose fit then the metric 2mm x 33mm will provide a tighter fit. In this case I recommend using the softer 50 durometer O-ring.


The mouthpiece opening O-ring (Item # 9A in the diagram):

The design nominal O-ring is a SAE -028 (in 70 durometer).

If it feels loose or there are any signs of a leak then the metric O-ring will provide a tighter fit.

The recommended metric O-ring is either a 2mm x 35mm (or a 2mm x 34 mm works and it can be easier to install).

This O-ring slides past the mouthpiece opening in the outer tube (Item # 3). So make sure that the inside edge od the opening has a smooth chamfered edge, not a sharp edge. After assembly, operate the DSV and check that the O-rind stays in place, in the groove, while fully opening and closing the DSV.


The two circumferential inner tube O-rings (Item # 9B in the diagram).

These O-ring can be either a -030 or a -029.
Either one works fine since this is not a sealing O-ring. These O-ring are not intended to create a seal, they are intended to create a constant gap between the two cylinders and create a bearing surface for sliding, with just enough friction so that the DSV has to be intentionally rotated. The gap is designed so that the two cylinders are do not slide and scrape on each other.

This O-ring are intended to keep sand or dirt from getting in between the tubes, but it is not intended as a water tight seal. The space between the tubes is a wet space and it has to be a flooded space.

There is a vent hole below the mouthpiece opening in the outer tube (Item # 3). Any attempt to seal the space between the tubes to keep it dry, by plugging this vent hole is a very bad idea. That could create a sealed void that will not equalize with the ambient pressure as you dive. Please, never consider closing the vent hole with a plug. It is not a good idea to create a sealed void.

The vent will also allow you blow the little amount of water in the mouthpiece tube before opening the DSV. By blowing the water from the mouthpiece tube, you can keep the hose-loop dry.



To disassemble the DSV:

Remove the retainer screw (Item #11) and rotate the inner in the closing direction and little past it so that the opining in the inner tube is far from the opening in the outer tube. Then slide the inner tube sideways. Only slide the inner tube sideways when the opening in the inner tube is far from the Opening in the outer tube, to avoid pinching or cutting the O-ring.

To assemble the two tubes just revers the process. Make sure the opening in the inner tube is not lining up with the opening in the outer tube. The inner tube opening should be facing up, near the label.


Lubricate all O-ring with good quality silicone grease. I do not recommend using any of the oxygen compatible grease. They do not work as well for this application and they are not needed.

[luis]

You can also find a lot of discussion on this subject on this thread in ScubaBoard:

https://scubaboard.com/community/thread ... st-9950382