"Not just a dust cap" cap
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It depends on the regulator. One common exception is the Atomic regulators which have a feature they call a Seat Saving Dynamic Orifice. Because the second stage seat is open when unpressurized it allow water into the system, possibly into the hose and first stage. This is especially a concern when connected to a stage or bailout bottle that is turned off at the cylinder during the dive. Some servo-assisted second stages are also prone to leak water in when unpressurized.
OP
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I use the ones used on the older Conshelfs and SEAs, look the same as those posted above. I get them new from Amron Int. IIRC they are around $4 each. They have a groove for O ring. I put them on all my regs except my MK17s.
Why not the MK17??
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Dust Caps
The original US Dives regulators did not have dust caps, It was well into several generations of SCUBA that the dust cap was developed and offered as standard equipment on newly purchased regulators or as and aftermarket accessory.
Prior the that time most diving and certainly dive manufacturing was concentrated in LA & Orange county California (see: wwwportagequarry.com ~~Legends of diving; Orange County did you know?)
The divers of that era in SoCal determined they needed a dust cap - event though it was not officially offered by the big diving manufactures so they improvised -- #3 or #4 black rubber medical/ scientific stoppers were brought in to play by the diving community. It was and still is unequaled as a "Slopper Stopper" as they were often called prior to acquiring the more marketable name of "dust Cap"
They were and are the best made best sealing least expensive slopper stopper ever devised--, They are certainly inexpensive and with out question seal the regulator.
I have always used them and at this late date will always use them as do may wife , son and grand children
Perhaps some of you with much better computer skills than I can look then up and post a picture or two on the board
SDM
@Dano -- note
The original US Dives regulators did not have dust caps, It was well into several generations of SCUBA that the dust cap was developed and offered as standard equipment on newly purchased regulators or as and aftermarket accessory.
Prior the that time most diving and certainly dive manufacturing was concentrated in LA & Orange county California (see: wwwportagequarry.com ~~Legends of diving; Orange County did you know?)
The divers of that era in SoCal determined they needed a dust cap - event though it was not officially offered by the big diving manufactures so they improvised -- #3 or #4 black rubber medical/ scientific stoppers were brought in to play by the diving community. It was and still is unequaled as a "Slopper Stopper" as they were often called prior to acquiring the more marketable name of "dust Cap"
They were and are the best made best sealing least expensive slopper stopper ever devised--, They are certainly inexpensive and with out question seal the regulator.
I have always used them and at this late date will always use them as do may wife , son and grand children
Perhaps some of you with much better computer skills than I can look then up and post a picture or two on the board
SDM
@Dano -- note
Thanks, Sam!
They sound perfect. I'll do a little sleuthing
They sound perfect. I'll do a little sleuthing
The earlier “dust caps” like the one posted in the pictures by @northernone are the best. The O-ring will seal like any other regulator O-ring. But they also have to be serviced like any other face O-ring. I actually replace that O-ring more often than many of the regulator O-ring. And like someone mentioned, if the O-ring is missing they will not seal.
The dust cap uses the old style K valve fat O-ring (-112), which happens to be the same as in a DIN fitting. The modern tank yoke valve normally uses the skinnier O-ring (-014). If you put the skinnier -014 O-ring in this dust cap it may seal, but it will fall off.
Note: we used to call this type of dust cap the “witches hats”. I think you can figure out why.
So, the good news is that the two new dust cap links shown have somewhat similar dust caps and they will be just as water tight.
Now for the bad news.
The first one is very minor. All the ribs that are shown in the picture for the NSS and Leisure-Pro are a minor inconvenience because they hold water. Again just a minor inconvenience because they are outside.
The second issue is what I find totally annoying. Some of these new dust caps (not all) are molded with a recess cavity on the inside face just inside of the O-ring groove. The cavity is just a pocket and it is sealed from the outside when the dust cap is in place. So the dust cap is still water tight, but that cavity can will hold water if it is not fully dried before installing the dust cap.
To dry this cavity requires the careful use of compressed air from your cylinder. And I mean careful because that cavity can hold more than just a few drops of water and because of the shape the water can be blown into the wrong direction.
The flat dust cap (as shown in @northernone pictures) can be easily dried with very little air or even with a dry towel. That is not the case with this new style of dust caps, if they have the recessed cavity. Again, you may get lucky and find some of the ones that do not have the recess.
I have thought about filling that recess with something like RTV or similar, but instead I just use that style of dust caps for some of my vintage display regulators and I use the vintage dust caps in my diving regulators.
If someone finds a reliable source for that style of dust caps without the cavity please let us know.
I will try to post a picture of the dust cap with the cavity later.
Thanks
The dust cap uses the old style K valve fat O-ring (-112), which happens to be the same as in a DIN fitting. The modern tank yoke valve normally uses the skinnier O-ring (-014). If you put the skinnier -014 O-ring in this dust cap it may seal, but it will fall off.
Note: we used to call this type of dust cap the “witches hats”. I think you can figure out why.
So, the good news is that the two new dust cap links shown have somewhat similar dust caps and they will be just as water tight.
Now for the bad news.
The first one is very minor. All the ribs that are shown in the picture for the NSS and Leisure-Pro are a minor inconvenience because they hold water. Again just a minor inconvenience because they are outside.
The second issue is what I find totally annoying. Some of these new dust caps (not all) are molded with a recess cavity on the inside face just inside of the O-ring groove. The cavity is just a pocket and it is sealed from the outside when the dust cap is in place. So the dust cap is still water tight, but that cavity can will hold water if it is not fully dried before installing the dust cap.
To dry this cavity requires the careful use of compressed air from your cylinder. And I mean careful because that cavity can hold more than just a few drops of water and because of the shape the water can be blown into the wrong direction.
The flat dust cap (as shown in @northernone pictures) can be easily dried with very little air or even with a dry towel. That is not the case with this new style of dust caps, if they have the recessed cavity. Again, you may get lucky and find some of the ones that do not have the recess.
I have thought about filling that recess with something like RTV or similar, but instead I just use that style of dust caps for some of my vintage display regulators and I use the vintage dust caps in my diving regulators.
If someone finds a reliable source for that style of dust caps without the cavity please let us know.
I will try to post a picture of the dust cap with the cavity later.
Thanks
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Hi Sam
I remember seeing several regulators with rubber stoppers and even a few with a cork style of stopper. This was in the early 70’s, when I started working at the dive shop in Puerto Rico. Some of the rubber stoppers had just a hole drilled across them to attach a lanyard, but if I recall correctly some looked a bit fancier with a narrow waist where the lanyard was attached and didn’t fall off.
I am pretty sure that at least one of the cork stopper was a modified wine bottle cork, but it has been a long time since I saw it.
Then Scubapro came out with a solid rubber ball. I personally didn’t like any of the solid rubber stoppers because they seem to take a set and I just didn’t trust them when they got too deformed. I do know that the solid rubber balls that Scubapro used did leak when they got old and took too much of a set. They tended to get hard.
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