Looking to Buy a Rebreather

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Honestly, when I got my Fathom I insisted on an ADV because I was so used to having one. However, as I said, I pulled the ADV out of my unit after a friend had a failure with the same ADV on her X-CCR (and since then I know another person that had the same failure on the X, and rddvet's wife had the same failure on her Fathom). Even without the ADV I still have two ways to add gas (MAV and BOV) and I found that this works fine, even on hot drop dives where I'm descending at 100' per minute - like I'll be doing this weekend (again) in SoFla.

I have to agree with @kensuf I hate ADVs but maybe I just haven't found the perfect one. I found the ADV on the rEvo sucked (apparently it's better now) so I turned it off and the SF2 one was super annoying if you were heads-up on surface so I kept it permanently isolated. I only ever used the SF2 ADV in class. The Defender I just bought doesn't have an ADV which suits me perfect.

My friends who are on X-CCRs have not had an issue with theirs as of yet but it is actually one of the questions that I first asked them.

I just hammer on my dil MAV all the way down for a hot drop. Even pointing a scooter straight down on the trigger I've never felt I had an issue adding gas to my loop. I have not really used an ADV in 6 years and am personally happy without one. One less failure point / potential leak for me.
 
Unless you're doing photography, or something else that requires silence, I would stick with open circuit for basic recreational diving. There's a risk/reward tradeoff with diving CCR's, for doing a simple 90' no deco reef dive, I would go with a single AL80 on open circuit almost every single time.

Why? That's your opinion. What risk? You didn't mention any facts. Like you said it's 90' and there is always BO. Just more work for a CCR lol
 
And as a newbie still in the excitement stage of CCR, I'll take a chance and differ with you. Since I've been doing nothing but CCR for the last year trying to build hours for each stage of training, I've been doing lots of warm water boat dives, both deep and shallow, and a smaller number of cold water shore dives.
Doing it over and over and over, the setup is getting automatic. Since I'm a stickler for checklists, I don't think I'm getting complacent.
So the safety piece of the risk/reward equation I can live with.
But the reward piece? Wholly apart from the improved reef dive experience now that I'm quiet, I relax a lot more. I'm not sweating the approach of turn pressure, and trying to relax more or ascend a bit to stretch my gas. I relax because I AM relaxed about gas. I can go as long as I care to, within reason, as long as I don't exceed what my AL40 offers me for bailout, which is essentially any dive with less than 20 min TTS. So what if I incur a few minutes of deco? Doesn't matter!
Me, I'm loving it!
Now I've got a dive-my-socks-off trip to Bonaire sched for September (I hope!) where I'm going to be OC only. I'll let you know if I change my mind.

Couldn't read a better response. I'm excited. Just need the funds LOL
 
I get logging time to get familiar with the unit while working towards more advanced diving. That's not what I was discussing. Also, I don't care what anyone says, 20 minutes of deco is not a recreational dive and well outside of what I was describing - recreational, no decompression diving.

If a person is motivated to stick to simple recreational dives, open circuit is the safer and easier option. Period.

Makes sense. I want to do it for more bottom time and eventually some day cave. For me, it makes way more sense to go into a cave or Wreck with a rebreather then on OC. If something happens, you have much more time to figure things out then if you were on OC. For normal recreational diving as you state, I agree
 
Why? That's your opinion. What risk? You didn't mention any facts. Like you said it's 90' and there is always BO. Just more work for a CCR lol
The risks? The 3 Hs
Hypoxia, hyperoxia, hypercapnia

Plenty of people die with BO seemingly right there.
 
as long as I don't exceed what my AL40 offers me for bailout, which is essentially any dive with less than 20 min TTS.
Is that a BO of air? correct me if im wrong but i think youll need more than an al 40 if your controller is showing 20min TTS on set point of say 1.2
 
Absolutely right. I was unclear. "Where my bailout shows 20 min TTS." At setpoint 1.2, my max CCR TTS would have been about half of that prior to bailout, assuming stress. At nominal consumption, it almost works out: maybe 16 min. Stupid to plan for.
My point was merely that modest B/O gas offers some significant latitude for rec/light deco diving.

The 1.3cu ft per min TTS was stuck in my mind from doubles diving min gas planning. And that's just for my RMV and dives <150' for bottom time <60 min at GF 50/70. Awhile back, I ran 50 scenarios and was surprised at the consistency of gas requirement per min TTS. Rock bottom quickly became 2 (or 4) CF per minute of TTS for 1 (or 2) divers. Easy to keep on a slate, converted to psi with whatever cushion you want.
"Dive until the TTS hits the equivalent Rock Bottom psi remaining"

:tlaphijack:
 

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  • TTS Gas Requirement.xlsx
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Why? That's your opinion. What risk? You didn't mention any facts. Like you said it's 90' and there is always BO. Just more work for a CCR lol

I believe the fatality statistics are something like CCR divers have a 10x time increased risk of dying underwater than open circuit divers. DAN can provide those numbers.

The failure modes in open circuit are pretty straightforward and usually result in continuing to get air while you're heading to the surface. The only real exception that I can think of is an HP seat failure on a downstream reg. Even a cut LP hose will still result in one of the second stages being able to deliver air while the tank is being drained rapidly.

The failure modes in a rebreather can be silent and kill you. Some of the rebreather failure modes lead to hypoxia and hypercapnia, both can cause serious confusion, blackout and death. Generally speaking, these aren't concerns for OC divers, especially not OC divers on non-decompression recreational dive profiles. Hypercapnia can be caused by something as simple as a bit of debris in a mouthpiece getting stuck in a mushroom valve (I've seen that happen twice), an o-ring that was missed on assembly (also seen that happen), scrubber breakthrough, accidentally installing the wrong insert, etc.

In my opinion, rebreathers add a level of risk that is unnecessary for a simple dive.

YES: I agree that if you're adding hours it may make sense to do a simple recreational dive on the unit.
YES: I agree 100% that if you're new to a rebreather you should be diving them almost exclusively for awhile to get intimately familiar with the unit, so it may make sense.
YES: I agree that there's the concept of mastering a tool and always diving the same config to have muscle memory.

However, if you're goal is to simply stick with recreational, simple, non-decompression dives - don't buy a rebreather. Save that $12k (unit cost, travel, training) and spend it on a nice liveaboard vacation instead.
 
However, if you're goal is to simply stick with recreational, simple, non-decompression dives - don't buy a rebreather. Save that $12k (unit cost, travel, training) and spend it on a nice liveaboard vacation instead.
Totally agree on this. Imo one should compare CCR accidents with OC Tech accidents. CCR diving is totally different from OC Rec diving and requires a completely different mindset. Most if not all Rec divers (and some Tech divers including CCR divers for that matter) I know do not have the right mindset to dive a CCR safely.
 
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