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I won't go into it in much detail, but specifically for cave diving I don't believe it's a wise idea to have your first experience diving oc in a cave be as you bailout. There are nuances to cave diving that vary slightly between oc and ccr. I was cave certified for almost 10 years before I went to ccr cave. I'm very glad I didn't start as a ccr cave diver. I've been helitrox certified for a while and plan to move to full trimix soon (only held off due to having a pfo). Rather than learning on the ccr, I'm taking oc trimix (tech 1) because I and most of my mentors believe in both tech and cave diving you need to hone your skills first on OC. But those are just my opinions based on my experience. I will leave it up to any instructors who want to wade into the waters of that discussion. I think in N. Fl you will find 90+% of instructors would tell a student to go OC first.

When I did my original rEvo training, I asked my instructor (who is also a cave diver) this question. I.e. do I need to do OC Cave first, before going CCR Cave? Her answer was "once you're diving a rebreather, why would you EVER go INTO a cave on OC?"

More recently, I have been starting to prepare myself for cave training. I currently do not even have Cavern training. I have spoken with Joe Citelli and Mel Clark. They both have no problem taking me on as a student for CCR Cave, even though I have no OC cave training. I'm not saying either one of them would take just any CCR diver as a Cave student without OC Cave experience. I believe for both of them, it depends on their assessment of the individual. But, it seems clear (to me, anyway) that the subject is not as cut-and-dried as "you have to do OC Cave first."

I do not at all mean this is as some back-handed way of patting myself on the back when I say that I think a diver can develop very good OC buoyancy without going through an OC Cave class. I mean that generally. There are plenty of OC tech divers with excellent buoyancy and trim that have not taken a cave class. So, why should OC Cave be REQUIRED as a prerequisite?

I think your statement that 90% of instructors would tell a student to go OC first may possibly be exaggerated. Maybe that is 90% of the instructors in your personal circle?

One instructor I talked to basically said "as a CCR cave diver, you don't need as good OC buoyancy as you would if you were an OC cave diver. If you have to bail to OC in a cave, then it's an emergency and you are just getting out. You're not trying to run a reel, etc.." You are not doing the things that test your buoyancy like you would be if you were an OC cave diver.

I don't take any of that to mean that you could pass a CCR Cave class with **** OC buoyancy. I assume a CCR Cave class would include doing at least one BO OC exit. And that you would have to demonstrate ADEQUATE OC buoyancy during that exercise in order to pass the class. It just seems to me that your OC buoyancy does not have to be AS top notch as it needs to be for an OC Cave diver.
 
Revo potted electronics...

If you completely flood the unit, e.g. loop was severed, you'd (obviously) loose the cells, but aside from cleaning the connectors, nothing else would be lost.


Revo III lungs: one benefit of the Revo is being able to wipe down the lungs and clean out the lung butter and properly dry them out.

Do think I need to look into having a cloth in the exhale lung. Thus far have resisted as I really don't want something that could interfere with the ADV should the cloth move around.

I used to dive with a cloth in the top, then stopped after I was told rEvo HQ says "no cloth in the top". Only just went back to it this past week.

I have never found my cloth out of position at all. I'm not worried about it affecting the ADV. For that matter, I generally try to dive without ever activating the ADV - and usually succeed. If the ADV somehow stopped working during a dive, I think would find a way to survive. :)
 
@stuartv , one thing I've learned from OC cave diving is a healthy respect for how much gas you need when there is an issue and how quickly a limited supply dwindles when you are far back and "agitated". I use the term agitated because that's how I've felt at times after hours of diving when I'm sweaty, hungry, and thirsty and it's a long long way to my deco bottles and even longer to the surface.

A friend took zero to Hero Cave CCR. It was a giant "trust me" dive that took him to places that had very real world potential to have a very bad day if something happened to his instructor. He didn't have the experience or muscle memory to deal with being lost (hadn't even done a black out drill). He's a great diver with a solid head on his shoulders, sadly he hasn't realized yet how bad things could quickly.

The mentality I see from zero to hero ccr cave divers is a belief that "I have all the time in the world to figure it out" if there is a problem. Vs cave divers who learned on OC that understand "I have the rest of my life to figure it out".
 
When I did my original rEvo training, I asked my instructor (who is also a cave diver) this question. I.e. do I need to do OC Cave first, before going CCR Cave? Her answer was "once you're diving a rebreather, why would you EVER go INTO a cave on OC?"

More recently, I have been starting to prepare myself for cave training. I currently do not even have Cavern training. I have spoken with Joe Citelli and Mel Clark. They both have no problem taking me on as a student for CCR Cave, even though I have no OC cave training. I'm not saying either one of them would take just any CCR diver as a Cave student without OC Cave experience. I believe for both of them, it depends on their assessment of the individual. But, it seems clear (to me, anyway) that the subject is not as cut-and-dried as "you have to do OC Cave first."

I do not at all mean this is as some back-handed way of patting myself on the back when I say that I think a diver can develop very good OC buoyancy without going through an OC Cave class. I mean that generally. There are plenty of OC tech divers with excellent buoyancy and trim that have not taken a cave class. So, why should OC Cave be REQUIRED as a prerequisite?

I think your statement that 90% of instructors would tell a student to go OC first may possibly be exaggerated. Maybe that is 90% of the instructors in your personal circle?

One instructor I talked to basically said "as a CCR cave diver, you don't need as good OC buoyancy as you would if you were an OC cave diver. If you have to bail to OC in a cave, then it's an emergency and you are just getting out. You're not trying to run a reel, etc.." You are not doing the things that test your buoyancy like you would be if you were an OC cave diver.

I don't take any of that to mean that you could pass a CCR Cave class with **** OC buoyancy. I assume a CCR Cave class would include doing at least one BO OC exit. And that you would have to demonstrate ADEQUATE OC buoyancy during that exercise in order to pass the class. It just seems to me that your OC buoyancy does not have to be AS top notch as it needs to be for an OC Cave diver.

Those two particular instructors very much biased towards CCR, especially Mel, (I won't extrapolate because I don't want hate mail). They were both 2 of the instructors that in my head immediately pop up as being in the 10% in cave country that would tell a student CCR all the way. I have my opinions, but it's based on my experience as just a diver, not a diive professional. I think if you asked around this area what people think about going straight into ccr cave, most would likely tell you OC first. At least that's what I've been told when I ask in person. I actually would prefer to do my trimix training on ccr, since most of my triimiix diives will be on ccr and I dive ccr more nowadays. But 2 instructors I have a ton of respect for convinced me OC was the way to go ane their logic made a ton of sense. I think in regular OW tech, a little higher percentage would say it's ok to start on CC as compared to in the cave diving world.
 
One instructor I talked to basically said "as a CCR cave diver, you don't need as good OC buoyancy as you would if you were an OC cave diver. If you have to bail to OC in a cave, then it's an emergency and you are just getting out. You're not trying to run a reel, etc.." You are not doing the things that test your buoyancy like you would be if you were an OC cave diver.
.

Sorry to double post, but it was easier. I wholeheartedly disagree with that thought process and for me personally it would be a red flag about that instructor, but that's me.
As for my 90%, it's a guesstimate, but not based on people I'm buddies with. I have actually asked that question to a large number of cave instructors in cave country and the students of some of the ones I never see in person. It could be lower like 75%, but it's definitely not a 50/50. I do believe as you saiid, it is a sliding scale. If a student has years of CCR OW experience, an instructor would be more likely to go for CC cave as opposed to someboyd that's moderately new to CCR, but is wantiing to do the cave class cc.

Edit: I actually stepped away for a moment and though more about that comment about not needing as good OC skills when you have to bail out to oc and it scares the cr-p out of me. That is an idiotic and dangerous statement. Please don't choose that instructor as your cave instructor.I would hate to meet that instructor in a small, silty passage.
 
Sorry to double post, but it was easier. I wholeheartedly disagree with that thought process and for me personally it would be a red flag about that instructor, but that's me.
As for my 90%, it's a guesstimate, but not based on people I'm buddies with. I have actually asked that question to a large number of cave instructors in cave country and the students of some of the ones I never see in person. It could be lower like 75%, but it's definitely not a 50/50. I do believe as you saiid, it is a sliding scale. If a student has years of CCR OW experience, an instructor would be more likely to go for CC cave as opposed to someboyd that's moderately new to CCR, but is wantiing to do the cave class cc.

Edit: I actually stepped away for a moment and though more about that comment about not needing as good OC skills when you have to bail out to oc and it scares the cr-p out of me. That is an idiotic and dangerous statement. Please don't choose that instructor as your cave instructor.I would hate to meet that instructor in a small, silty passage.
I’d echo the above. Saying you’re on your way out, it doesn’t need to be as polished is asinine.
 
Thanks for posting that. Excellent to get some thoughts from somebody who owns a rEvo and other units.

I do have some questions/thoughts.

First, the rEvo did not make your Top 4. Is that just because of the flood (in)tolerance? Or also factoring in what you called their Apple style of not letting you do certain repairs yourself? Or more to it in feeling like those Top 4 of yours are preferable to you over the rEvo?

On the rEvo flood tolerance, have you had legit problems with your rEvo that would have been a non-problem if you had a way to de-water it? How many times have you had to end a dive early because of water in the loop, where you could have continued if you could de-water? I'm asking because I'm still trying to understand how big of a problem the rEvo "flood tolerance" really is. Is it a problem on paper? Is it a problem that screws people over often? Or is it a problem that causes 1 dive in 1000 to be ended early and that's about it? Here, I'm just trying to understand your personal experience with this issue.

You mentioned that none of the rEvo electronics are potted. I would have said all of my rEvo electronics are potted. The "brain" circuit board is potted inside the battery box. The O2 and solenoid boards are each potted inside the modules that live in each of the counter lungs. But, my unit is a hybrid, with DiveCAN, a solenoid, and rMS. You said you have an mCCR, so yours is fully manual. No DiveCAN, no solenoid, and no rMS. Is that a difference between the rEvo mCCR versus hCCR/eCCR?

It comes down to the fact that I don't want to be facing 3-4 hour+ deco obligation or swim out of a cave when something as simple as a torn mouthpiece can fully flood the rEvo. Granted that is a low risk but the risk is still there. If I had a way of de-watering the loop from a slow or minor flood then I'd simply stay on the unit and continue to de-water it. For MOD3 type dives my goal is stay on the loop as long as possible if it's not compromised due to a CO2 breakthrough or full caustic flood.

In the ocean my dives are rarely over 2-2.5 hours. Logistically I can carry enough bailout for that. I'm simply swimming a couple hundred feet back to mooring/shot line and ascending. In a cave it's pretty typical to have a 3000-5000ft swim before I can go up and still have to complete deco. I'm carrying a **** ton of bailout in a cave. I regularly sidemount LP95s pumped to 3800 and I carry and/or drop additional AL80 stages but it's still a bad day if you truly need to bailout that far back in a cave. I suppose Manatee Springs is another example, you can be over 10,000ft back there. I have not been that far back myself there yet but it's another potential example.


EDIT: I realize I didn't fully answer your question regarding rEvo flood tolerance. Truthfully I never had to end a dive because of flooding on my rEvo but I also wasn't doing that much cave diving or dives longer than 3 hours.

The single worst flood I had on my rEvo was when I was brand new post-MOD1. I was walking up the boat ladder in heavy seas in North Carolina and did not have my DSV closed and my loop went underwater. It was the last dive of the day but the unit would not have been dive-able I had plenty of caustic water in both scrubbers at this point. This would have probably have been non-issue on the SF2 and any unit with T-pieces with counterlungs that function as a water traps (I could be wrong).

I had other dives on rEvo where I had enough water in my top exhale counterlung/scrubber to be caustic but it never made it to the second inhale lung or bottom scrubber and I did not have to end or call the dive.

Personally I'm not doing the 6-8 hour dives or even the 10-12 hour dives that KUR / WKPP people are doing however I am doing 3-4.5 hour dives regularly now. I'd like to slowly start itching into the 5-6 hour dive territory this winter it's just a lot of commitment, a lot of deco but I want a unit that can be de-watered for these types of dives. For 3 hour dive..I dont really care that much about de-watering abilities that much but that's just my personal opinion.

My main example would be on my SF2. I had a small torn mouth piece that slowly flooded my loop. You wont really detect a torn mouthpiece with a stereo check and of course the unit will still pass positive/negative. It was really a non-issue I was able to dewater my loop and my scrubber stayed dry. Due to the length of my dive I don't feel this would be safe on a rEvo and I've had a large amount of water in my top scrubber.

My other example was the stock SF2 DSV is ****. The gasket they use to seal the lever knob swells and will slowly leak allowing water into the unit if it's not tight. I replaced the SF2 DSV with something else but I've had water ingress on a dive from here.

My information regarding the rEvo electronics might be outdated as I'm solely using antiquated rEvo II mCCR with no RMS or solenoid or battery box. By not potted I mean the fisher cable and rEvo dream cables going into the top of the unit are simple PG7 glands into a bulkhead. If I destroy a cable these are not potted into the head. I can simply unscrew the PG7 gland and install a new cable. I realize the battery box and RMS are probably potted but these could simply be removed from the unit and it's still dive-able with some modifications. You could just send those parts back to rEvo for repair. For my SF2 or Defender I have to send the entire head back for service. There is no easy way for me to swap out the cables going into the head.
 
Do think I need to look into having a cloth in the exhale lung. Thus far have resisted as I really don't want something that could interfere with the ADV should the cloth move around.

Like @stuartv I keep a small shammy in my exhale lung even though it's not recommended or approved by the rEvo HQ. You have to be careful not to put pressure on the seam in the counterlung there. Personally I don't use the rEvo ADV so it doesn't bother me.
 
It comes down to the fact that I don't want to be facing 3-4 hour+ deco obligation or swim out of a cave when something as simple as a torn mouthpiece can fully flood the rEvo. Granted that is a low risk but the risk is still there. If I had a way of de-watering the loop from a slow or minor flood then I'd simply stay on the unit and continue to de-water it. For MOD3 type dives my goal is stay on the loop as long as possible if it's not compromised due to a CO2 breakthrough or full caustic flood.

Mouthpieces: I have never had a torn mouthpiece or had to replace a mouthpiece. But, after about 30 hours on my rEvo, I did decide I wanted to ditch the gag strap/mouthpiece. So, then I had to find a regular mouthpiece for it. What I found is that just about every mouthpiece available to me to put on it was not really big enough. They would fit, but by stretching them beyond the size for their intended usage. I could definitely see where, had I stuck with one of those, it would have torn eventually. I did eventually find that I could get a JJ mouthpiece and that fit without seeming to be overly stretched. However, I only dived it a few times and then decided I prefer the stock mouthpiece and head strap and went back to that since.

So, what I'm wonder is, if you are using the correct mouthpiece, is the possibility of a torn mouthpiece *really* something to base your choice of rebreather on?

Also, FULLY flooding a rEvo from a torn mouthpiece seems like a bit of a stretch? Unless it tore and the loop came out of your mouth and floated freely for some time while open?

In the ocean my dives are rarely over 2-2.5 hours. Logistically I can carry enough bailout for that. I'm simply swimming a couple hundred feet back to mooring/shot line and ascending. In a cave it's pretty typical to have a 3000-5000ft swim before I can go up and still have to complete deco. I'm carrying a **** ton of bailout in a cave. I regularly sidemount LP95s pumped to 3800 and I carry and/or drop additional AL80 stages but it's still a bad day if you truly need to bailout that far back in a cave. I suppose Manatee Springs is another example, you can be over 10,000ft back there. I have not been that far back myself there yet but it's another potential example.

You kind of make that sound like diving one of your Top 4 (instead of a rEvo) would somehow allow you to carry less BO?

Or, you're saying that you feel like there is a greater chance of having to make an OC exit on a rEvo than one of the others. Again, I have to wonder if that is a realistic concern or an "on paper" concern? Not that you couldn't have to make an OC exit. You could - but you could on any of them. The question is whether there is actual data - not just theory and anecdotes - that support that idea that an OC exit is more likely on a rEvo than one of those others.

EDIT: I realize I didn't fully answer your question regarding rEvo flood tolerance. Truthfully I never had to end a dive because of flooding on my rEvo but I also wasn't doing that much cave diving or dives longer than 3 hours.

The single worst flood I had on my rEvo was when I was brand new post-MOD1. I was walking up the boat ladder in heavy seas in North Carolina and did not have my DSV closed and my loop went underwater. It was the last dive of the day but the unit would not have been dive-able I had plenty of caustic water in both scrubbers at this point. This would have probably have been non-issue on the SF2 and any unit with T-pieces with counterlungs that function as a water traps (I could be wrong).

I had other dives on rEvo where I had enough water in my top exhale counterlung/scrubber to be caustic but it never made it to the second inhale lung or bottom scrubber and I did not have to end or call the dive.

Personally I'm not doing the 6-8 hour dives or even the 10-12 hour dives that KUR / WKPP people are doing however I am doing 3-4.5 hour dives regularly now. I'd like to slowly start itching into the 5-6 hour dive territory this winter it's just a lot of commitment, a lot of deco but I want a unit that can be de-watered for these types of dives. For 3 hour dive..I dont really care that much about de-watering abilities that much but that's just my personal opinion.

My main example would be on my SF2. I had a small torn mouth piece that slowly flooded my loop. You wont really detect a torn mouthpiece with a stereo check and of course the unit will still pass positive/negative. It was really a non-issue I was able to dewater my loop and my scrubber stayed dry. Due to the length of my dive I don't feel this would be safe on a rEvo and I've had a large amount of water in my top scrubber.

My other example was the stock SF2 DSV is ****. The gasket they use to seal the lever knot swells and will slowly leak allowing water into the unit if it's not tight. I replaced the SF2 DSV with something else but I've had water ingress on a dive from here.

My information regarding the rEvo electronics might be outdated as I'm solely using antiquated rEvo II mCCR with no RMS or solenoid or battery box. By not potted I mean the fisher cable and rEvo dream cables going into the top of the unit are simple PG7 glands into a bulkhead. If I destroy a cable these are not potted into the head. I can simply unscrew the PG7 gland and install a new cable. I realize the battery box and RMS are probably potted but these could simply be removed from the unit and it's still dive-able with some modifications. You could just send those parts back to rEvo for repair. For my SF2 or Defender I have to send the entire head back for service. There is no easy way for me to swap out the cables going into the head.

I see what you mean on that last bit.

Also, thank you for taking the time to respond as you have. I realize my comments in this post may sound like I'm trying to argue with you, but I am not. I am just trying to fully explore and understand the weaknesses and risks of the unit I'm diving. You have MANY more hours on the loop and on rEvo in particular compared to me. So, I really, REALLY appreciate any little tidbits and insights I can get from you.
 
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