First Rebreather Purchase - Lots of Questions

[rjack321]

My Meg instructor is diving a pathfinder, that unit looks and acts really good in the water. Here in Eu it's regularly being dived to 120 meters with 4 hour run times in cold water. And ready to dive with 2*3l tanks it's one of the lightest rebreathers I have seen (around 20 kg with a canister light and 2l argon tank)
Since it's been discontinued there is a lot of used units for sale. The problem with Pathfinder (and Meg 15) is that wires in the head don't last long so unless you know how to handle a soldering iron you will be paying someone to replace them every few years, considering you are so close to ISC that really should not be a problem.

Why? The scrubber bed depth on the pathfinder is not the same as on the 2.7 and Meg15, which is why the canister is narrower. Leon specifically rates the pathfinder to 60m because of this issue. Since there actually are ISC units that are rated to 100m+, to suggest such a gross deviation from the manufacturer's usage recommendations (which is also 3 times deeper than the recreational dives the OP planned on doing) seems rather silly.

 

[stuartv]

It looks as though most people scour the interwebs for months on end to finally land on two and then flip a coin on which rebreather they land on. Im hoping I can give a few bits of information and some tried and true experts on this forum can help me narrow the search while my wife will still let me make this purchase.

1. Currently diving with a Shearwater Perdix computer - which I thoroughly enjoy but am not 100% married to
2. Want the ability to travel with
3. Not really into tech diving - looking more for extended bottom times - super deep is not a big concern, but Id like to still have options down the road

Hopefully this narrows the field a bit.

Thanks!

I've been diving CCR for less than 6 months and only have 20 hours on the loop, so take my thoughts with that disclaimer.

After reading what a lot of people here on SB have to say about different units and about learning to dive a CCR, I decided that whatever I bought for my first unit should be considered my "starter unit". I.e. it is what I will learn to dive and then eventually figure out what I *really* want.

I am a big advocate of buying used. If you shop well and buy a used unit, you can do your training and learn on your unit, then sell it later for little or no loss - assuming you decide later you want something different. At that point, you'll have to pay a bit more to do a crossover to a new unit, but that should be way less expensive than the initial training. And you'll have the benefit of additional breadth of experience...

I got my rEvo (with all Shearwater electronics) for under $5K, ready to dive. I have seen a fair number of used Prism IIs (with Shearwater electronics) for $3500 - 5K.

I haven't weighed them, but I dive double steel 120s when I dive OC. My rEvo, with an AL40 for BO, FEELS a lot lighter than my 120s...

I have talked to several CCR instructors who are proponents of going straight from OC, single tank, recreational diving, to CCR - as opposed to putting OC tech training in as an intermediate step. Most people seem to agree that going from OC to CC is like learning to dive all over again. So, why not do it sooner, rather than later? I am not a CCR instructor and I did OC tech training first, so I am not advocating either path over the other. And my opinion should not be given much weight, considering my very light amount of experience.

Like many, I did my research, chose my unit, and now I recommend what I have. But, it's all I know....

That said, there are a couple of aspects of the rEvo that I think are especially relevant to your stated desires.

It's a hybrid unit. That means that you can buy it as a pure manual unit, or you can buy it with fully automatic electronics. But, even with fully automatic electronics, it still has a Constant Mass Flow Orifice, which is constantly flowing O2 into the loop. That makes it very easy to fly manually. You can leave the electronics on the Low Set Point (normally 0.7) and fly it manually, with the electronics just there as a backstop in case you get distracted and fail to maintain your ppO2 properly. Other units offer the same thing. What makes the rEvo especially nice in this regard is that, with the CMF, you have to manually inject O2 much less often. If the CMF orifice and Intermediate Pressure is setup right, and if you are being perfectly still and not working at all, your ppO2 will basically hold steady without any manual adds and without the solenoid firing.

On my unit, we tested it during my training. I started with my ppO2 at 0.70. I held onto a platform and stayed as still as I could for 10 minutes. At the end, my ppO2 was 0.67. I really like that feature. When I start taking pictures while on CCR, I am hoping that I can spend extended periods waiting for "the shot" without having to move my hand to manually inject and without having the (slight) noise of a solenoid firing.

The rEvo III Micro has a titanium chassis and is pretty compact. And all rEvos are very low profile because of the scrubber design. My understanding is that the Micro is very travel-friendly.

The rEvo rMS (rEvo Monitoring System) is a temperature probe system for monitoring your scrubbers and letting you keep track of how long you have left until you start to get break-through. It won't tell you if you have channeling or what the CO2 level is in your body. But, it is still nice to have a system that lets you extend the time on your scrubber with some peace of mind. Meaning (simplifying here, for the sake of discussion), the factory says the scrubber is good for 4 hours. Without rMS, if you use the sorb in your scrubber for somewhere close to that, you would need to change it (all). With rMS, you might see that, after 4 hours, you are still only using the sorb in the 1st basket. So, you could keep diving, with some confidence. Or, just replace the sorb in the top basket, instead of all the sorb in both baskets. Like I said, that is a simplified view of rMS, only described to make the point that it is a nice feature (to me, anyway).

Last point: Diving on a CCR is awesome. I don't want to dive OC at all any more. But, if your purpose is simply extended time at recreational depths, and still doing recreational dives (i.e. no mandatory deco stops), you should just keep in mind that CCR is not magic. If you're diving deeper than, say, 60 feet, being on CCR will give you longer NDLs, but they aren't THAT much longer. If you are diving deeper and limited to "no deco", a CCR is not going to give you hugely longer bottom times.

OTOH, if you are diving shallower, where you are running out of gas way before you run out of NDL, then yes, a CCR will give you WAY longer bottom times. But, as noted, a set of doubles would be a LOT cheaper and may meet all your needs.

You said you're in the PNW, so I suspect your dives are deeper. So, just be aware - a CCR limited by NDLs is not going to make a HUGE difference to your bottom times. On dives with square profiles, bottom time will actually be pretty close between OC and CC. Multi-level profiles will give a bigger advantage to CCR, though.

 

[wedivebc]

@wedivebc I'm not entirely sure that it is "sad" that the Apecs electronics have been discontinued given that the Tiburon has come out with industry standard electronics these days....
Not having stood them next to each other, is the Pathfinder that much smaller than the mini Meg?

I am more saddened by the discontinuation of the pathfinder. Comparing a mini meg to a pathfinder is like comparing an al 65 tank to a 40cuft. It's slimmer and taller. For deeper stuff the meg probably breathes better but you can't beat a pathfinder for travel. Leon tells me the Shearwater electronics just won't fit into a pathfinder head.

 

[wedivebc]

Why? The scrubber bed depth on the pathfinder is not the same as on the 2.7 and Meg15, which is why the canister is narrower. Leon specifically rates the pathfinder to 60m because of this issue. Since there actually are ISC units that are rated to 100m+, to suggest such a gross deviation from the manufacturer's usage recommendations (which is also 3 times deeper than the recreational dives the OP planned on doing) seems rather silly.

Actually it's more than just the scrubber bed depth it has to do with the overall geometry, length:width ratio which is not optimal but was required in order to get a 5lb scrubber into such a slim package. Also look at the void space between the scrubber and can. That space works out to just 1"square which is the minimum area of any breathing passage throughout the pathfinder. There were a few tradeoffs in order to get it that small.

 

[tbone1004]

I am more saddened by the discontinuation of the pathfinder. Comparing a mini meg to a pathfinder is like comparing an al 65 tank to a 40cuft. It's slimmer and taller. For deeper stuff the meg probably breathes better but you can't beat a pathfinder for travel. Leon tells me the Shearwater electronics just won't fit into a pathfinder head.

The more accurate statement would be "I don't want to bother with making the Shearwater Electronics fit into the pathfinders head". If you have actually seen the size of the boards, you'd know it's more a lack of desire from ISC's part than a lack of capability.

@JonG1 Martin is only over here for relatively short stints, only in cave country, and typically only teaching cave. While the lungfish looks pretty slick and I would love a chest mount unit for deco/IWR use, I think it's going to remain obscure enough that I wouldn't recommend a normal individual to purchase it in the US.

@ccmurphy2005 IMO the best piece of advice you've been given, and one that I regularly advocate for was from @doctormike and somewhat from @stuartv . To reiterate, take the mod1 class first. Make sure that the CCR experience is something you want to invest in. There are three MAJOR advantages to that.
First, it lets you choose the instructor independent of the unit. This was important for me because I wasn't sure which unit I really wanted to invest in, new I wanted to dive CCR, and knew that Ted McCoy was one of the best CCR instructors in the world. I got lucky in that I was given a Meg and he still has one of the prototype Meg's so it suffices to say he has a bit of experience with it, but I got lucky with that. The CCR that I will end up using is not a unit he teaches on, but in terms of learning how to dive a CCR, the unit itself is pretty irrelevant.
Second, it lets you figure out if CCR is really what you want to do with your diving before making a wicked big investment.
Third, is it makes try-dives useful. If you don't know how to dive a CCR properly, a try-dive really isn't going to tell you if you want to dive that particular rebreather because you aren't diving it properly enough to experience the nuances. The task loading of trying to deal with buoyancy, trim, and paying attention to your ppO2 is going to keep your attention from "feeling" the unit, how it breathes, the ergonomics, etc.

There are two downsides to doing that. If you decide to not get the unit you were trained on, you have to pay for a crossover course which is typically around $500 so while you are choosing the instructor based on their credentials, if you have two that are "tied" but one teaches the unit that you "think" you are going to like, or if the instructor teaches multiple units, it probably behooves you to choose the unit you think you will like. Second was mentioned as well which is renting a unit which is an added cost unless you have a buddy that will loan you the unit. With most units, the instructors are also dealers, and if you use an instructors loaner unit then buy a CCR from them, they will usually deduct the rental cost from the purchase price of the unit so that can be a wash. It can also be mitigated by buying a used unit then reselling if you end up going in a different direction.

 

[stuartv]

Third, is it makes try-dives useful. If you don't know how to dive a CCR properly, a try-dive really isn't going to tell you if you want to dive that particular rebreather because you aren't diving it properly enough to experience the nuances.

I think a try-dive can be very useful even before doing MOD 1.

I did a try-dive on a DR O2ptima way before I got any actual training on diving CCR.

I agree that I didn't know enough to appreciate the nuances. But, it DID let me experience breathing on a loop, under water, and experience the (relative) silence. It let me experience how much lighter a CCR is, compared to my double 120s.

The try-dive was enough to convince me that I DID want to invest in diving a CCR. I liked the quiet and the feeling that I did not have to worry about running out of breathing gas. It was also enough to convince me that I did NOT want to invest in an O2ptima. I did not like how tail-heavy it was. I was in a 7mm wetsuit, had 12# of weight mounted on the very top of the unit, and I still sculled CONSTANTLY to try and keep my feet up in some semblance of horizontal trim. I also did not like how the over the shoulder counter lungs filled up my peripheral vision.

Now, I have a rEvo and normally dive it with no weights at all (unless I'm in a drysuit) and get good, flat trim with no sculling. And I only have the loop hose itself in my peripheral vision.

Again, the real point here is that I think a try-dive before any training CAN be very useful. Just not for the same things as try-dives after you have training.

I would also say that if you do a try-dive and you don't like it, you should do more try-dives on other units. One unit that you don't like doesn't necessarily mean you won't like CCR diving on a different unit. But, if you try-dive a unit and DO like it, then, now you know. It's probably something for you to invest in pursuing further.

 

[reddiver970]

Last point: Diving on a CCR is awesome. I don't want to dive OC at all any more.

That's exactly how I feel !

 

[doctormike]

I think that a try dive is fine to see if you are interested, but it's also possible that you may get turned off the idea, when it's really just a bad try dive for some reason.

I don't think that it's a good idea to do a bunch of try dives with the idea that you will buy the unit that you like best on those trials, and then get trained on it.

 

[stuartv]

I think that a try dive is fine to see if you are interested, but it's also possible that you may get turned off the idea, when it's really just a bad try dive for some reason.

I don't think that it's a good idea to do a bunch of try dives with the idea that you will buy the unit that you like best on those trials, and then get trained on it.

I pretty much agree. I was not trying to suggest doing try-dives to choose your unit for long-term commitment. Like @tbone1004 said, at that point, you don't really have the ability to assess the nuances. I was only suggesting that try-dives COULD help you decide if you want to pursue CCR at all or not. And, like I said, if you don't like one try-dive, you should try other units (and maybe other instructors) before you give up. If you try several and don't like any of them, then maybe CCRs are not for you. If you just try one and don't like it, then, like you said, it might have just been a bad try-dive, or it might be a good try-dive, but on a unit that is not for you for whatever reason.

You just need one good, enjoyable try-dive to know that you want to pursue it further (though you could still ultimately find that CC is not for you for some reason).

Also, one would want to be careful about ruling out a particular unit based on a try-dive. I ruled out the DR, for me, and I still think my reasons were good ones (for me).

But, after my first 2 days of training on my rEvo (1 in confined water, and 1 in open water), I can say that I might have ruled the rEvo out, too, if that first day or even two had just been try-dives. After day 1, I was feeling like the unit was kind of hard to breathe. After the next day (in open water), I got out REALLY feeling like CCR diving at all just might not be for me. Fortunately, on day 3, things clicked and my mind turned around 180 degrees. From then on, I had no doubts about continuing and it has only gotten better, since, as I have learned more and dialed my setup in more.

So, some judgment is important if one does a try-dive and wants to rule out a particular unit based on that. Your reasons might be solid, or they might be things that will change if you get the full training and some experience. As well, some reasons that seem valid for choosing a unit might turn out to be negatives, later, after more experience.

Thus why I feel like any unit should be treated as a starter unit. Even with MOD 1 training and 20 hours of experience under my belt, it still seems like not enough to really evaluate multiple units and make any better of a choice than I already did. And thus, my feeling of doing some try-dives and research and then taking a plunge on a well-researched used unit. Just doing MOD 1 on a rented or borrowed unit does not seem like enough experience to then think you can make a nuanced decision by doing try-dives on other units.

I don't think MOD 1, by itself, is enough for someone to be a competent, skilled CCR diver. At least, it was not enough for me. It's the license to learn, to go and BECOME competent and skilled. And, until you are truly competent on one unit, I'm not convinced you can really evaluate the nuances of other units to decide what you REALLY want to use long-term.

 

[jgttrey]

Agree with all of what tbone said. I'll add another reason why you might want to train before you buy, which is it that you'll be able to figure out if, in fact, a rebreather is something you really want to buy at all. Since you seem to primarily want a unit only to enhance your recreational dives, you may find that it is not the solution you hoped it would be.

Bear with me for a moment as this may have relevance to you. I'm getting there.

I really have a foot in both camps. I love diving CCR and the additional capabilities it offers for the kind of technical diving I like to do. I also like it recreationally, provided the extra concerns pointed out below are not too great.

But, I also have a family of recreational divers, including young ones. When diving with my kids, and basically serving as a personal family DM, I do not dive the CCR. I think it is a bad idea from a safety standpoint and it is much more task loading, both on the surface and underwater, than I want to undertake when my time is better spent helping them.

How does this (maybe) relate to you?

CCR diving is great, but, it isn't always the best choice, particularly if you're basically doing recreational dives and your buddies are all OC:

• Unless your buddies are on CCR or technical OC, you are limited to their dive time anyway.
• For very shallow dives, particularly if you are with OC divers zooming up and down, you will find CCR can be a bit of a pain, as you are constantly fiddling with loop volume.
• It is more work. Fun work, for me, but time consuming nonetheless to set up the unit, pack sorb, sterilize the loop, tweak gear, analyze gasses, label tanks, etc. On tech trip, it's fine bonding time with your buddies. With the family, I don't want to be farting around with my rebreather while they are at the beach or waiting on me for dinner. It's also a ton of stuff to haul around compared to a single tank rig.
• The number of dive ops that support rebreathers is far more limited. If you insist on diving CCR, it will impact not just your choice of operator but your choice of destination. For example, if I want to dive my CCR in Cozumel, I either need to use a different op than everyone else in my group, or I would need to go through some considerable hassle to arrange for sorb and fills, or bring a booster, etc. It just isn't worth it for recreational diving.

That's a long way of saying it isn't always that easy or convenient to dive CCR recreationally. Sometimes, it's just easier to strap on an 80 and dive. If you want to dive longer, sidemount and strap on 2.

I also firmly believe that diving a rebreather is a bit like flying a plane. You need to do it often and you need to be diligent about keeping your skills up. I'm fortunate to be able to dive mine often even though I cannot dive it exclusively. But, a rebreather is not like OC where it is relatively easy to not do it for a year or two and jump right back in. The unit requires maintenance as do your skills. You need to seriously assess whether or not your particular type of diving, buddy group, destinations, etc., lend themselves to diving a rebreather on a consistent enough basis to make it safe, and worth it.

So, I would take a hard look at whether your intended use is realistic and training before you buy is a prudent way to do that. Rebreather diving is not just "enhanced OC," it is a whole different thing and usually there needs to be a reason for it to justify the cost and hassle. Don't get me wrong. It is a great fun, but if i were only doing my family diving, it would not be a worthwhile investment for me.