Confusion about Poseidon Xstream DIR/GUE compliance

[Gyula Fora]

Hi!

There seem to be several threads floating around discussing whether poseidon regs are dir compliant or not.
I have been diving the newer generation xstreams for some years now and it seems to me that there is very little one can say today against its dir/gue compliance.

In the past people have argued agains poseidon for the following reasons: non-standard hoses, upstream design/fail-shut behaviour, non-standard IP, impossible to repair underwater

These arguments seem to not hold at all for the newer generation Xstream regs:

1. They work with any standard hose (simple hose adapter)
2. While it's an upstream second stage it is practically impossible to fail shut (like any downstream reg)
3. IP range of xstream first/second stages is about the same as any other popular reg on the market (e.g. scubapro)
4. Xstream 2nd stage cover is easily removable by hand

In addition my experience is that these regs are extremely reliable and almost never fail.

The only concerns I have with these regs and DIR are somewhat different than what other people are saying:

1. While the OPV on the first stage will let you breath normally during some 1st stage failure scenarios, it can also hide some serious problems that might be hard to notice without a freeflow and might lead to quick gass loss. This seems to be a problem mostly in backmount where the first stage is behind your back.
2. Purge button is in non-standard position so out-of-air diver cannot purge
3. Reg might free-flow during valve drill after the initial burst of air coming from the 2nd stage

Do you think these are valid concerns and are enough to make a reg non dir-compliant? Any experience with poseidon regs in first stage failure scenarios?

Thank you!

 

[tbone1004]

@Gyula Fora with this, I am not a DIR diver, and I do dive Poseidons

1. it is still an adapter which can be seen as an "extra failure point"
2. the upstream issue is a holdover from the days of true upstream tilt valves that would lock shut. They won't lock shut, but they do get rather hard to breathe with IP creep. Gas loss is arguably less bad with an OPV than it would with the normal second stages because there is no venturi assist like on a normal second stage and the OPV won't freeze shut where a second stage can freeze open in cold water
3. the IP issue is from the Cyklons which required 165psi vs. 135-145psi for "normal" regulators, and the IP for the Xstream is ideally 123. It will work on 135-145 but doesn't breathe nearly as well as it should.
4. The arguments against Poseidon are pre-xstream. Cyklon was always easily removable as shown by its preference with sump divers, but the Jetstream is very much not. Not that it ever really needs to be, but it isn't.

1. what problems is the OPV going to hide? You can hear the bubbles come out most of the time, and if not, you're diving DIR so your buddy should notice it for you.
2. purge button placement can be overcome quite easily but an OOA diver can still very much purge
3. Keep the diaphragm up, mouthpiece down, or reg in your mouth and it's a nonissue. It is annoying during valve drills though.


The issue really is whether your instructor won't let you use them for a DIR style course, or if you are on a DIR project and can't use them. I asked this question to Casey McKinlay who is over the WKPP a year or two back and one of the other arguments was team uniformity which is definitely a nice perk when out in the woods of Florida and you have something go sideways. Minimizes the amount of spares you have to carry.

The question really is why does it matter to you? The Xstream MK3 is arguably the best regulator made to date and is near perfect *if it had a 5-port swivel turret which is coming in the next generation, it would be IMO perfect*. If it works for you, then why does it need to be DIR compliant?

 

[Gyula Fora]

The question really is why does it matter to you? The Xstream MK3 is arguably the best regulator made to date and is near perfect *if it had a 5-port swivel turret which is coming in the next generation, it would be IMO perfect*. If it works for you, then why does it need to be DIR compliant?

Thank you for the quick and exhaustive answer! It's a very good point that the OPV might actually preserve gas in many cases.

I just find it rather annoying that people seem to dislike poseidon regs on the ground of arguments that might have been valid a decade ago but definitely not today. Just wanted to make sure that I am not missing anything

 

[Caveeagle]

The question really is why does it matter to you? The Xstream MK3 is arguably the best regulator made to date and is near perfect *if it had a 5-port swivel turret which is coming in the next generation, it would be IMO perfect*. If it works for you, then why does it need to be DIR compliant?

^^Yes..
A 5th port is coming? Put me down for two please!

 

[tbone1004]

@Caveeagle they're coming at request of the military customers they have. Still in design phase so I would be surprised to see them before 2020, but they're coming.

@Gyula Fora the arguments against them were for a very specific type of diving and a very specific group of divers. Whether those arguments were ever valid outside of that group is a different discussion.
I believe that the arguments against the Cyklon which are only valid for the high IP were never that good. They've proven incredibly reliable with sump diving which is arguably the hardest on regulators of any kind of diving out there.
Sheck used Jetstreams as have many others in the early parts of cave diving. At that time, hose adapters were not available and were incredibly expensive. There were huge supply problems for Poseidon with various US distributors so the motivation to make them work for that style of diving was very low. Jetstreams do have an upstream valve and were largely misunderstood at the time, but more importantly they do not have a removable cover *doesn't stop me from using them exclusively*, but can be a problem and more importantly were deemed finicky to tune. Yes they are finicky, especially compared to a "normal" scubapro style second stage, but the convenience of them being finicky is a singular movable part, incredible WoB, and surprisingly easy to service.

With the Xstream MK3 *which I admittedly don't own because I am cheap and purchased about a dozen Jetstreams for pennies on the dollar*, it takes the valve design from the Jetstream but greatly improves the case design, and then improves the initial design from the 3960 first stage with the sphere. I do truly believe it is the best designed regulator on the market, but I'm too cheap to buy them ;-)

 

[decompression]

I think anyone that is so focused on a specific brand of reg is missing the big picture of DIR. I’ve never turned anyone away because of a specific piece of equipment. I choose inform, educate and help people make reasonable and informed choices.