When should I get a rebreather?

[khacken]

Is it best to get some good caving experience before I go rebreather or is it preferred to get on RB as soon as you can? I know that I will definately go RB one day, but I want to make sure I am not going too fast down that path.

I am Intro to Cave right now with 20 cave dives/ 250 total dives.

[atedeschi]

I just got rebreather certified and I am glad I did. It was like a been doing it in a previous life, I did not find it hard or compilicated at all. I am still going to dive it a few more hours before I go in the caves with it, but I think that is just a mental thing. I been diving for 9yrs, a Tec Instructor, OWSI & cave certified, to give you an idea of my experience. This being said I had not problems in the class, buoyancy wasn't an issue at all, and all me required skill I completed in the second dive of my class. But a lot say they had trouble with things. I think if you do your training tec in OC, you will gain the proficencey you need and then go to CCR. Just make sure you have your skills down in OC first, no need to rush into it.

[Gary]

It seems to me that a RB has a break even point on gear about the single stage level and becomes advantageous when multiple stages becomes the dominate form of diving.

Even then death rates on RB seems to be several times the rate of OC.

The primary advantages for RB seems to be in deep / mixed gas diving.

The move to RB purely on "neato factor" should probably be avoided. When OC gear volumes begins to enter multiple stages on a regular basis and/or adequite bailout volumes for deep diving enters the same range RB can begin to become a serious consideration.

Attention to gear is probably more important / time consuming than in OC. Mixing OC and RB teams is probably not a good idea. Making sure the RB switch fits not only your needs but the needs of the divers you will be in the water with.

IMO

[FW]

Gary makes some excelent points, but you can't even take the Rebreather Cave course, until you have several hours (25?) in open water on a rebreather.

[Diverlee]

Gary makes some excelent points, but you can't even take the Rebreather Cave course, until you have several hours (25?) in open water on a rebreather.
I say if your going to dive CCR only do it now and get lots of practice. If your going to go back and forth get more time on OC Thats just my opinion. I do both.

[jkaterenchuk]

You might also want to clearly understand what training and retraining you will do to do and pay for when moving from OC to CCR. In many cases you OC certification is not accepted if your diving CCR.

John

[w ripley]

The primary advantages for RB seems to be in deep / mixed gas diving.IMO

I thought your post had several good points, but my buddy and I went to RBs primarily because of our cave dives, or their durations. On OC we found ourselves planting stage bottles everywhere, breathing down 3rds in, 3rds out, pulling bottles and refilling them and doing it all over again. Our minimum cave dives were about 90 minutes and our longer dives were exceeding 240 minutes, and we wanted to go farther. Lots of gear on OC, as you can imagine.

The RB offered the ability to dive over 10 hours, without using any of the gas in our stage and bailout bottles. No, we haven't done a 10 hour dive, nor do we plan on doing one, but it's nice to know that we've got the time should we have a major problem (LED lights are matched to the duration of the RB).

So, deep diving is great on a RB and the amount of HE we're using is pretty small. That's a plus, for sure. But, for cave diving the RB has a lot of plusses.

I will admit that my profile seems a little bigger, as going thru restrictions at Cow are a little harder. Other than that...

[pwl4476]

I think that Bill makes a good point. The CCR/RB carries its own safety factor for unexpected circumstances. Silt out, no big deal, you can wait a long time. CCR/RB diving is more distance limited than it is duration limited, meaning, as long as you don't exceed the distance/time of your bailout, you can stay down for a long time. You could, say make 20 laps around the Expressway circuit at Ginnie without concern, as long as your bailout will get you back from anyplace on the circuit.

For long distance dives, there's not much benefit in terms of gear, because you have to carry the bailout for a safe return, and that can be a fairly decent number of cylinders, much the same as OC, except you only breathe them in emergency. In fact for most of my dives, I'm more loaded down with cylinders than I was for an equivalent distance OC dive.

For me the benefit is not having to get geared up but one time per day. Make a long duration dive and that's it for the day. I'm a lazy diver, but a religious preparer, which is a must for CCR. My post dive prep for the next dive is usually about an hour, which is usually done while others are having a beer.

Paul

[aainslie]

One thing to think about is, you need to understand OC to do CC, but the reverse is not true. If you bailout, you're essentially OC, and you'd better have planned that bailout with a clear understanding of your SAC rate. Also, OC failure modes are pretty simple - find another reg connected to an independent gas source (possibly making it independent along the way) and shove it in your mouth. CC is more complex. Rather spend time with the lower emergency workload before adding complexity.

I think it really helps to get your OC skills down pat before going CC in a cave. I'd suggest waiting until comfortable with OC and stages before going CC - where bailout, once more, requires you to be proficient with stages.

[atedeschi]

I agree. I think you should have to do all your training in OC, then take the Mod1 CCR and you are set. Once you understand and have the skills in OC, you just need to learn how to use your CCR and get time on the unit. Then when you are comfortable move on to move advanced dives on the CCR. I don't believe you are going to get anything more out off Trimix CCR then if you did trimix oc and mod1 on your ccr.

[Luxrok]

I started to write a response and it grew to large for me to post here in good conscious. So, I created a blog post answering the question, When Should I Get a Rebreather? (http://www.quietdiver.com/477/when-should-i-get-a-rebreather.html)

This is no april fools post and I apologize for the change of venue.

Hans

[Marc Bryan]

Copied from above LINK...

Typical OC Cave Dive
Entrance: $10.00
Fuel: $10.00
Fills: $12.00 (3 Single 80's with Fill)
Total: $32.00

Typical CCR Cave Dive
Entrance: $10.00
Fuel: $10.00
B/O Fills: $8.00 (2 Single 80's with Fill)
O2: $12.00 (12cuft)
Dil: $3.00 (19cuft)
Sorb: $30.00
Total: $73.00

I am assuming that this is based on Air not Nitrox for the OC. If Nitrox (which 90% of the divers here use) the fills would be $24.00 so that would add to they OC cost.

I do not count the B/O because I almost never use it. I could amortize it over several dives and get it down to less than $0.25 per dive, so you should take that out of the cost.

$30.00 in Sorb? That seems at least 2x higher than it would cost here.

Do you use the entire $12.00 of O2? For a three hour dive I wouldn't think so. And even if you did, here in Fl it would only cost you about $4.00

If I were to do the numbers based on a dive at Peacock (shallow depth and low/no flow) it would cost about $2 more to do the CCR dive, if I calculate consumables a little on the high side for the CCR. Certainly not $40 higher.

Just wanted to shed a different perspective on the costs if you were diving in FL. I totally agree with everything else on the blog post, and appreciate the time you took to write it up.

[Luxrok]

Thanks for giving us the North Florida perspective. If I were diving in Florida or NJ, it would be CCR for all the reasons you give. Here in MX, we have to live with a different cost basis. We have limited suppliers and strict import laws. Both of those drive up the costs.

You are right about the Bailout. Since I switch back and fourth, sometimes I have to fill my B/O.

As for the gas consumption, in the shallow caves you will be amazed at how much gas you can consume. Especially as a tourist. If you are not used to the saw tooth profile, you can easily chew up 1500-2000 psi of O2 in a dive. If you are new on CCR in the cave, you will consume more as you vent the loop repeatedly to try and control your bouyancy.

If we want to get into consumables, we can also amortize the cost of the three sensors, which would add a couple of bucks a dive. $210 for 3 sensors over 100/hrs/year equals about $6/dive.

Thanks for taking the time to read the post and comment. It is a worthwhile exercise for a newcomer to witness.

Hans

[khacken]

Thanks for the reply guys! Guess I will continue on with OC for a little while longer then, and just save up the money. I am quickly catching the cave bug, and some brakes are always a good thing.

[aainslie]

Hmmm... don't forget the MASSIVE depreciation on the rebreather. And if you have my addictions, there's also the cost of the endless tinkering and "upgrading". My rebreather costs me more like $200/dive.

But... the upsides are just so big on bigger dives, especially if you're exploring. Set up the bailout, then just keep returning over and over past those bottles without ever touching them. Entering the water for a 4-5 hour dive with just your sidemount cylinders. It's a wonderful thing.

Downside - little cave. It's hard to get back there on an RB. And some of the prettiest cave in FL is small.

[FW]

Downside - little cave. It's hard to get back there on an RB. And some of the prettiest cave in FL is small.
You just have the wrong rebreather ;)

[Luxrok]

Hmmm... don't forget the MASSIVE depreciation on the rebreather. And if you have my addictions, there's also the cost of the endless tinkering and "upgrading". My rebreather costs me more like $200/dive.

But... the upsides are just so big on bigger dives, especially if you're exploring. Set up the bailout, then just keep returning over and over past those bottles without ever touching them. Entering the water for a 4-5 hour dive with just your sidemount cylinders. It's a wonderful thing.

Downside - little cave. It's hard to get back there on an RB. And some of the prettiest cave in FL is small.

Andrew, The more I read your writing the more you make sense! For big dives, the CCR is only way to go. And I never amortize the cost of the unit and the tinkering. I am also constantly making tweaks and that stuff adds up.

Hans

[Martin Robson]

Some intersting costings on one of the posts. On a recent two week trip to France this is a rough calc on just one dive.

Depth 396 feet
Bottom time 36 mins
Total dive time in excess of 7 hours

O2 consumed 14.83 cu.ft
Trimix consumed 7.06 cu.ft
Dry suit inflation gas (air) 3.5 cu.ft
1 x scrubber fill
Rebreather batteries - nil, unit is rechargeable

I admit there were a larger number of bailout cylinders but those same stages were part of our dives every day every day for two weeks and are no back in UK and still full ready for the next trip.

I don't think CCR is as expensive as OC.

[amphipod06]

One thing to think about is, you need to understand OC to do CC, but the reverse is not true. If you bailout, you're essentially OC, and you'd better have planned that bailout with a clear understanding of your SAC rate. Also, OC failure modes are pretty simple - find another reg connected to an independent gas source (possibly making it independent along the way) and shove it in your mouth. CC is more complex. Rather spend time with the lower emergency workload before adding complexity.

I think it really helps to get your OC skills down pat before going CC in a cave. I'd suggest waiting until comfortable with OC and stages before going CC - where bailout, once more, requires you to be proficient with stages.

I totally agree with Andrew. A lot of the CCR divers I see are carrying 40 cf bottles...in caves!!!

On of the things you learn in OC is gas planning, in CCR cave diving you have to take into account the OC gas requirements for a bailout out of the cave, granted it is not 3rds you are talking about but you still have to plan for contingencies and account for your buddy as well, if that is how you plan. YMMV.

Dive safe,

Celia

[battles2a5]

Lots of good info on this thread. I am going to wait until 50-60 hours on my unit before I take it in the caves. But the 2 primary drivers for me getting one is a) deep dives and b) gas logistics. I live in NC and we usually have about a 40-50% (in a good season) of a trip making it out. If we get blown out we usually go down to cave country. I was really getting sick of dumping gas or blowing trimix on shallow dives and the amount of bottles that we had to lug around for a weekend of diving, to/from the car, into the hotel, etc. was getting ridiculous. Now w/ the rebreather I can cover pretty much any diving I want to do w/ a small set of BO bottles and a couple of dil choices, and I need to haul about a quarter of the gear for a weekend.

[icestac]

A lot of the CCR divers I see are carrying 40 cf bottles...in caves!!!

Nothing wrong with AL40s... it may just take a LOT of them for doing a real dive where a CCR makes sense. :)

But I've used 40's for taking the CCR in and putzing around the front of the cave (just to get some hours in on the unit and building up the confidence level) -- it would definately not be sufficient for a "real" dive.

Cheers,
Jeff

[Diverlee]

The few times I have taken my unit in the caves I used 2 AL40's instead of 1 AL80, for places like Peacock. In some caves I take 2 AL 80's. All depends on the dive plan, etc...

[sea2summit]

I’ve seen a few posts about size being a problem on CCR, I bet within 3 guesses I can get your CCR. There are better/smaller ones out there for caves. And as was already mentioned if you have a catastrophic failure with your unit you still have OC.

I had the pleasure of getting good and stuck in a cave this past weekend during a silt out and the thing that really settled me down and helped was this thought “I’m on a rebreather I have 4 more hours to figure this out then I have bail out after that”. I really respect the early explorers for being OC and doing what they did but my experience Saturday made all the cost of the CCR totally worth it.

[mattmexico]

yo

To have some cave experience before the ccr cave course has some advantages though.

Before enrolling into a ccr cave course you have to have a number of ccr openwater dives before being able to enroll into the ccr cave course assuring that your buoyancy skills and operation of unit do not distract you from learning how to cave dive.

When going through the ccr cave training you really need to get your buoyancy and trim down. Divers with a lot of open circuit experience could be the ones that have the biggest issues to addapt the ccr diving.

If you want to go ccr go do it, dive plenty in the openwater to get proficient and then go on to take a ccr cave cross over program.

greetings
Matt

[MedCop]

I went with my CCR in caves after we started doing 3+ hour dives on OC. I already had a rebreather and dove it ow, it only made sense to start diving it in caves.

[amphipod06]

Nothing wrong with AL40s... it may just take a LOT of them for doing a real dive where a CCR makes sense. :)

But I've used 40's for taking the CCR in and putzing around the front of the cave (just to get some hours in on the unit and building up the confidence level) -- it would definately not be sufficient for a "real" dive.

Cheers,
Jeff

Not a problem with that, I think to putz (is that really a word?) around the cavern a 40 cf is fine, I was referring to longer deeper types of cave dives.... 2X 40 cf's is fine in lieu of an 80 in a place like Pcock where you are never far from an air hole if you need it. :-)

Dive safe,

Celia