Regulator for tec

[Angelo Farina]

I agree with nearly all of this, Just not that a need for 3 first stages is “extreme”.

The third first stage is not "extreme": it is useful when you add a pony or deco tank.
However, many people do deco without an additional tank. An additional deco tank is useful only if contains highly-enriched nitrox, or even pure oxygen, which indeed are just for "very advanced" tech diving.
In my life I did a lot of deco simply using the air contained in the main twins. Here in Italy, most tech divers use a 15+15 liters twin, at 232 bars, which provides an enormous amount of air. There is really no need to use a third additional cylinder for deco, if you do not like (as me) to use accelerated deco with high oxygen PP.
With such a setup you can go down to around 60 meters maximum, with a reasonably long bottom time, and still you will have plenty of air for your long deco stops.
Beyond this are trimix and pure oxygen deco, which for me is really "too advanced" tech diving for a not-professional diver.
Regarding the usage of high oxygen pp for deco, I see that many favour this approach. But I did never consider it to be safe. Shortening the deco time thanks to high PP of oxygen has some inherent risks, but we would be off topic discussing them here.
To the OP I again recommend to proceed slowly, one step after the other. Just start with "light tech", which for me is the safest way of diving: limit the depth to 30-40 m maximum (so no big risk of narcosis), use an ample tank filled with air (usually a 15 liters single, 232 bars, is enough), you can do with just a single first stage in DIN attachment (or 2 first stages with yoke), and plan the bottom time to be "just beyond" NDL.
Most agencies recommend to plan within NDL, but at any minimum problem, if something bad happens, you end exceeding the NDL. And you are not ready, nor equipped for it.
In my opinion, it is safer to program the dive just beyond NDL, so you know that you must be prepared and equipped for a true deco stop. If for any chance you must end the dive earlier than planned, then you will be within NDL and you can surface directly. If everything goes as planned, you will make a true deco stop of just 5-6 minutes, corresponding more or less to the additional time you have got at bottom beyond the NDL.
Such a dive profile is now considered "tech", whilst 40 years ago it was considered fully recreational. And I always considered it safer than a diving profile just within NDL rec limits.
For this minimal tech level you do not need to spend a lot of money expanding your equipment, you can do that just purchasing the DIN converter, or a second first stage.
But of course it all depends what your "tech" buddies will want to do...

 

[Caveeagle]

The third first stage is not "extreme": it is useful when you add a pony or deco tank.
However, many people do deco without an additional tank. An additional deco tank is useful only if contains highly-enriched nitrox, or even pure oxygen, which indeed are just for "very advanced" tech diving.
In my life I did a lot of deco simply using the air contained in the main twins. Here in Italy, most tech divers use a 15+15 liters twin, at 232 bars, which provides an enormous amount of air. There is really no need to use a third additional cylinder for deco, if you do not like (as me) to use accelerated deco with high oxygen PP.
With such a setup you can go down to around 60 meters maximum, with a reasonably long bottom time, and still you will have plenty of air for your long deco stops.
Beyond this are trimix and pure oxygen deco, which for me is really "too advanced" tech diving for a not-professional diver.
Regarding the usage of high oxygen pp for deco, I see that many favour this approach. But I did never consider it to be safe. Shortening the deco time thanks to high PP of oxygen has some inherent risks, but we would be off topic discussing them here.
To the OP I again recommend to proceed slowly, one step after the other. Just start with "light tech", which for me is the safest way of diving: limit the depth to 30-40 m maximum (so no big risk of narcosis), use an ample tank filled with air (usually a 15 liters single, 232 bars, is enough), you can do with just a single first stage in DIN attachment (or 2 first stages with yoke), and plan the bottom time to be "just beyond" NDL.
Most agencies recommend to plan within NDL, but at any minimum problem, if something bad happens, you end exceeding the NDL. And you are not ready, nor equipped for it.
In my opinion, it is safer to program the dive just beyond NDL, so you know that you must be prepared and equipped for a true deco stop. If for any chance you must end the dive earlier than planned, then you will be within NDL and you can surface directly. If everything goes as planned, you will make a true deco stop of just 5-6 minutes, corresponding more or less to the additional time you have got at bottom beyond the NDL.
Such a dive profile is now considered "tech", whilst 40 years ago it was considered fully recreational. And I always considered it safer than a diving profile just within NDL rec limits.
For this minimal tech level you do not need to spend a lot of money expanding your equipment, you can do that just purchasing the DIN converter, or a second first stage.
But of course it all depends what your "tech" buddies will want to do...

I understand your point. I started cave diving in the early 90s and most of that was as you describe. Double backmount 104cf tanks with air (21%). We did plenty of deco on air using navy tables and Aladin Pro computers. We began to use Nitrox 32% for deco, but still just stayed with air tables, finding it was just an added margin for safety.

Fast forward to 2016-2020 and things are very different. Divers are taking Nitrox right alongside open water training. Most of our local shops bank Nitrox(32%) and getting an “air” fill is somewhat unusual. You get into deco pretty quick in some of our local 90-100’ caves diving air. A little less exposure on 30-32%, but by the time you are training at the full cave, (or advanced wreck) level, you should expect to see decompression.

with the available training, and access to gas mixes, I don’t see why anyone around here would pursue decompression diving without high %o2, or 99%o2.

of course things vary by region and support available.

for the op.. you need to talk with a local instructor and find out what gear they recommend.

..I would be pretty surprised if very many are still teaching air deco as a best practice.

 

[Angelo Farina]

with the available training, and access to gas mixes, I don’t see why anyone around here would pursue decompression diving without high %o2, or 99%o2.

As said, this is a bit off topic. However, very shortly, I am quite sure that any kind of "accelerated" deco brings you far away from safety. The more accelerated, the less safe.
There are a number of factors pointing in this direction:
1) the amount of Nitrogen you have to release before being able to surface is given by the dive profile, so it is fixed when you begin the deco. If the deco is shorter, the flow rate of Nitrogen through your body and veins is necessarily higher. And this increases the risk that there are large bubbles, which can be trapped somewhere.
2) usually DCS is caused by your "critical" tissue, the one where Nitrogen has been stored with larger concentration. Such a tissue is not necessarily in direct connection with your blood, so he could not "know" that you are breathing pure oxygen. In almost all the mathematical models employed for calculating deco times, each tissue releases the excess Nitrogen at a rate proportional to the difference between the partial pressure inside the tissue and the partial pressure of the gas in your lungs. But this is true only if all these tissues "see" what is in your lungs. Some tissues are very far from them, in between there are other tissues which possibly trapped little Nitrogen, but are acting as a filter between the critical tissue and your blood-lungs. So these critical tissues will degas with the same speed as if you was breathing air, and you risk to not wait enough time at deco stops for degassing it properly. It is a remote risk, but why taking it?
3) And finally, carrying with you a deco tank containing a mixture with high PPO2 can be very dangerous if that mixture is breathed at depth, causing oxygen toxicity.
For these reasons I never reduce my deco times when enriched air or pure oxygen is available for deco. I always consider to be breathing air. And I never carry enriched-air deco tanks at depth, I consider them only as an useful additional resource if deployed by the boat attached to the deco bar when they see the divers approaching the surface.

 

[Matthijs]

@Angelo Farina Let me preface by saying I'm not an experienced deco diver, but the way I understand it is that bubbles form because of the pressure gradient between the pressure in your tissues vs the ambient pressure. If you replace the nitrogen content of the air you breath with oxygen instead, the pressure gradient stays the same, and therefore bubble formation is not impacted.

The reason why accelerated deco works is that your offgassing rate is dependent on the pressure gradient of the dissolved gas in your tissues vs the inert pressure of the gas in your bloodstream. If you replace nitrogen with oxygen, that gradient will increase and therefore make you offgas faster with the same bubble formation.

Regarrding your second point, I get that some tissues are slower because there is less blood flowing through them. Regardless, the rate of offgassing should still increase when you breath a higher ppo2 mixture, right? You

 

[fish149]

I'd suggest you forget SP if you're going tec. Get HOG or Deep Six. Going tec it's likely that you'll wind up with way more than 3 regs and you'll want to be able to service them yourself.

 

[LanceRiley]

the MK17 is a very capable first stage and could be used for technical diving, however, it is not ideal. I say that because it has 2HP ports and 4LP ports with no rotating turret. Hose routing on doubles is simplified when you have 2 HP and 5 LP ports on a rotating turret, like on the scubapro MK25. There are lots of manufactures that make make first stages in this configuration (deep6, HOG, Apeks, Scubapro, Mares, Hollis etc etc etc). Most folks recommend (not required just recommend) that you keep all your regulators the same models so that you can easily swap them, again that is convenience not required.

pics of mk17 hose routing...works but you can see a lot more potential for hoses getting bent to get them where you want them....
View attachment 570849

vs a first stage with a rotating turret and 5th LP port, the routing is just a bit cleaner.

View attachment 570850

I did not see that comming!

A gue diver told me that both 2nd stage will come from the right 1st stage. But i totally get you that each 2nd stage should come from individual 1st stage. That way there is redundancy.

 

[LanceRiley]

I agree with nearly all of this, Just not that a need for 3 first stages is “extreme”. It really just depends on what kind of diving the OP has in mind. One of the first “tech” classes will be advance Nitrox/ deco procedures (often combined in my area). You will need a third reg for this.

I do agree with the advice to proceed slowly! You do not need to buy all this at once. You could just get a matching mk17 and learn to dive doubles. Only point, is that when you start diving with other divers using double tanks... you are probably getting into deco territory unless you are staying very shallow.

Yes for doubles another mk17 but would it matter if i got a mk11 for the 2nd 1st stage? Its a bit cheaper i assume breathes same. We dive tropical. Then a mk2 for deco stage?

 

[LanceRiley]

I'd suggest you forget SP if you're going tec. Get HOG or Deep Six. Going tec it's likely that you'll wind up with way more than 3 regs and you'll want to be able to service them yourself.

Located in the philippines. I ve thought of the deep6 but i dont have the means to go get a deep6 maintenance class, no deep6 dealers here too

 

[LanceRiley]

The third first stage is not "extreme": it is useful when you add a pony or deco tank.
However, many people do deco without an additional tank. An additional deco tank is useful only if contains highly-enriched nitrox, or even pure oxygen, which indeed are just for "very advanced" tech diving.
In my life I did a lot of deco simply using the air contained in the main twins. Here in Italy, most tech divers use a 15+15 liters twin, at 232 bars, which provides an enormous amount of air. There is really no need to use a third additional cylinder for deco, if you do not like (as me) to use accelerated deco with high oxygen PP.
With such a setup you can go down to around 60 meters maximum, with a reasonably long bottom time, and still you will have plenty of air for your long deco stops.
Beyond this are trimix and pure oxygen deco, which for me is really "too advanced" tech diving for a not-professional diver.
Regarding the usage of high oxygen pp for deco, I see that many favour this approach. But I did never consider it to be safe. Shortening the deco time thanks to high PP of oxygen has some inherent risks, but we would be off topic discussing them here.
To the OP I again recommend to proceed slowly, one step after the other. Just start with "light tech", which for me is the safest way of diving: limit the depth to 30-40 m maximum (so no big risk of narcosis), use an ample tank filled with air (usually a 15 liters single, 232 bars, is enough), you can do with just a single first stage in DIN attachment (or 2 first stages with yoke), and plan the bottom time to be "just beyond" NDL.
Most agencies recommend to plan within NDL, but at any minimum problem, if something bad happens, you end exceeding the NDL. And you are not ready, nor equipped for it.
In my opinion, it is safer to program the dive just beyond NDL, so you know that you must be prepared and equipped for a true deco stop. If for any chance you must end the dive earlier than planned, then you will be within NDL and you can surface directly. If everything goes as planned, you will make a true deco stop of just 5-6 minutes, corresponding more or less to the additional time you have got at bottom beyond the NDL.
Such a dive profile is now considered "tech", whilst 40 years ago it was considered fully recreational. And I always considered it safer than a diving profile just within NDL rec limits.
For this minimal tech level you do not need to spend a lot of money expanding your equipment, you can do that just purchasing the DIN converter, or a second first stage.
But of course it all depends what your "tech" buddies will want to do...

Hes i realized going tec isnt going to be cheap. The tech class isnt immediate were rounding up buddies who wants in. Were being guided by a tech diver in our group. Hes all alone now as tech diver after his tech buddies moved to other locations. Hope fully wel be able to attend basic tech by end of the year. Were slowly getting the list of stuffs we need slowly. It gets quite expensive to get everything at 1 time. I live in a ccountry that has diving in the backyard. If we get our own boat and rent our own tanks without the dive package, we can easily dive for say 2 dives 30$ and thats including lunch lol. Iv had most of my first 100 dives this way. We had a padi divemaster buddy who just wanted to dive. He taught us a lot of things. There were 3 of them. Now theyve migrated to different countries. Weve decided to reactivate the group . So a couple of us padi rescue, are racking up experience for the newbies ..... hopefully theyl go tech too

 

[LanceRiley]

I understand your point. I started cave diving in the early 90s and most of that was as you describe. Double backmount 104cf tanks with air (21%). We did plenty of deco on air using navy tables and Aladin Pro computers. We began to use Nitrox 32% for deco, but still just stayed with air tables, finding it was just an added margin for safety.

Fast forward to 2016-2020 and things are very different. Divers are taking Nitrox right alongside open water training. Most of our local shops bank Nitrox(32%) and getting an “air” fill is somewhat unusual. You get into deco pretty quick in some of our local 90-100’ caves diving air. A little less exposure on 30-32%, but by the time you are training at the full cave, (or advanced wreck) level, you should expect to see decompression.

with the available training, and access to gas mixes, I don’t see why anyone around here would pursue decompression diving without high %o2, or 99%o2.

of course things vary by region and support available.

for the op.. you need to talk with a local instructor and find out what gear they recommend.

..I would be pretty surprised if very many are still teaching air deco as a best practice.

We have 1 tech diver in the group. And hes all alone now among the recreational divers. And has been our source of info. But again he.s been diving since 1984 so hes been through a lot. Ive been diving since 2011 but had a 5yr hiatus. Ive noticed him on single tank deep dives. Yes we dive 40meters on single tank with a bit of cave. Dont worry its a small cave. Probably just 20m inwards. His favorite deco gas is 50% nitrox. And ive noticed that with another tech diver in another group. Their deco gas of choice is 50% nitrox