Looking to Buy a Rebreather

[tbone1004]

@kensuf that is not where I would have expected to find it....

 

[stuartv]

I'm a OWSI with about 800 + dives. I am cavern certified and looking and researching rebreathers to see if it makes sense and what are my best options. I have about 50 + side mount dives. I am looking for more bottom time and perhaps cave in the future. I was looking at KISS since there are a few instructors in ohio that teach it. I am also a Scubforce Dealer and looked at the SF2 but the price seems high even for a dealer and I have heard a lot of negative comments about it (head up, head down breathing). What are your thoughts?

Nobody has mentioned rEvo. I know some of the posters that have already chimed in will knock the rEvo, but I'll throw it out for your consideration anyway.

Disclaimer: I have completed through MOD3 training (full trimix - 100m cert) on the rEvo, but I don't have any real experience with anything else and I'm not an instructor on any CCRs.

Pros:

- lower profile than any other CCR, I think. If you're looking where you're going (i.e. head up), then it's even lower profile (overall diver profile, that is) than a Choptima, I think. I guess a side mount rig would be lower profile, top to bottom, but obviously wider.
- a rEvo Micro is light. The Micros are all titanium cases. Very easy to travel with. I pack mine in a suitcase with 2 dog beds for padding and it comes in just under 50#.
- requires minimal lead to dive with. I wear my trilam drysuit with my medium warm undies (for 50F water) and use no lead at all.
- build/maintenance/cleaning is super quick and easy. My checklists are about 1/5 the length of my buddy's that has a Tiburon.
- Can use up to 5 sensors. There ARE times when this can be an advantage. Other than the cost of sensors, I don't know of any downside to this.
- Minimal connection points to fail and let water in. Not that you can't flood one. I have done it. But, I think the design is more resistant to flooding than other units.
- Can rig the harness Hogarthian-style and have a VERY clean/uncluttered front/chest. I only have the 3-button MAV block on my front (well, and the Shearwater controller on my left arm and the loop with NERD) that makes it any different than diving single tank back mount OC.
- Scrubber design makes it EXTREMELY unlikely that you would ever have channeling or bypass for a CO2 hit.
- Scrubber design allows much more efficient use of sorb. I.e. you don't end up throwing away NEARLY as much good sorb as with other designs. Especially if you have and use rMS.
- rEvo rMS (rEvo Monitoring System) monitors your sorb usage in real-time and lets you know how much longer you have until you need to cycle out the top scrubber basket or both scrubber baskets. The early days (over 10 years ago) of rMS were marred by rMS components that crapped out fairly easily. From what I can tell, the designs have been updated and the current rMS probes and electronics are solid.
- With the rEvo DiveCAN controller, you can have rMS and 3 O2 sensors. Then, with a NERD or rEvo Dream (which includes HUD), you can have 2 additional O2 sensors. These 2 subsystems can be COMPLETELY independent - no physical connection between the controller and its sensors and the monitor and its sensors. And the monitor subsystem (i.e. NERD or Dream) is completely analog inside the unit. No electronics at all, inside the unit, for the monitor system to depend on. Only the battery in the NERD (or Dream).
- The rEvo has a Constant Mass Flow orifice. It flows O2 in the loop at a constant rate, no matter your depth*. You tune the O2 reg Intermediate Pressure to match your metabolism and it gives you a MUCH larger margin of error (i.e. more time) on failures that would result in the loop going hypoxic. I can swim gently for several minutes before my pO2 drops 0.1 ATM. If I sit perfectly still and relax, my pO2 basically holds constant. If you run a low SP and fly it manually, this means you go much longer in between times of needing to inject O2. If you let the electronics have full rein of your pO2, then it means the solenoid fires a lot less often than units with no CMF or needle valve.
- The counter lungs are very well protected from damage. They are inside the metal box.
- The counter lungs on the Micro are pretty much the perfect size (for me). They are only barely bigger than what gives me optimal loop volume. So, if I screw up and let my loop get too full, it's not nearly as bad getting a full loop on other units that have much larger CLs. Also, if the Micro CLs are too small for you, rEvo has a very inexpensive kit of spacers that make the case a bit thicker, allowing the CLs to expand more and give you the same CL volume as the rEvo Mini - which should be MORE than enough for anyone.
- You can get the rEvo with or without a BOV. I have it, but I have not used it (in OC mode) at any serious depth. However, when I have tried it, it does seem to breathe reasonably well. rEvo claims that their BOV breathes better than their DSV (which is the Draeger) and they do (from what I understand) have an ANSTI machine, and have measured the WOB themselves.
- The 3-button MAV block is nice. Meg diver/instructor friends have looked at mine and said "I wish my Meg had a 3-button block like that."
- Has a factory stand option (with completely customizable height), which is very easy to take on/off for travel and provides nice rings for clipping stuff to.
- Dive-Tronix is the U.S. Shearwater repair facility. They are also a factory-authorized rEvo (and Meg) service facility. That means you have a one-stop shop for getting a rEvo fully serviced - the unit itself and its electronics. And Dive-Tronix does awesome work, has great prices, and super fast turnaround. And they are awesome people in general.
- Mares bought rEvo. Dive Gear Express is a Mares and rEvo parts dealer. That means that, generally, rEvo parts are very "available" in the U.S..
- I have purchased 2 used rEvo III units, with Shearwater controllers and rMS, in the last 3 years or so. The most I paid was $5K. I bought a Mini first, then got a good deal on a Micro and bought that (and sold the Mini) for the lighter weight (better to fly with).
- There are several rEvo instructors in FL now and at least one that is willing to come and do training at Lake Jocassee (in SC). Lake Jocassee offers any depth needed for anything from OW to Adv Trimix, you don't get blown out, you can get trimix fills there (but make sure to arrange in advance to ensure there is helium there) and the boat rides are cheap...
- I have found my units to be pretty straightforward to work on myself - even for things like replacing the battery box (which contains the brains of the unit), the O2 and solenoid boards, etc.. I think about the only thing I haven't done myself is replace a counter lung (which I would not even attempt - that is something I would absolutely send it off to have done, if needed). Fortunately, even my Mini, from 2009, did not need either CL replaced during its 10-year service.
- if you want a NERD, you can use a NERD with a Fischer cable attachment, or a NERD with the 4-pin wetmate connector. rEvo offers the appropriate cable that gets installed into the unit, connected to the O2 sensors, to support either type of NERD. I bought my NERD with a Fischer connection and then later had Dive-Tronix change my NERD over to the 4-pin cable (at my expense, of course).

[too long, continued in next post]

 

[stuartv]

Cons:
- Once you get water in the loop, there is no way to get it out during the dive. Fortunately, one, the rEvo has many less ways to get water in the loop than a lot of other units. There are no T-pieces on the breathing hoses. And there are only 2 breathing hoses, total. And, two, the rEvo will hold a fair bit of water in the loop before it actually becomes a problem. Also, I did a BO ascent from 270 the other day (as part of MOD3 class). Burped the loop (open and close the DSV while out of my mouth) repeatedly on the way up. No (more than the usual, minimal) water in my loop after the dive.
- If you are in GUE trim (i.e. perfectly flat) the work of breathing is not great. But, if you are in "cave trim" (i.e. head up just enough so that the top of your head is even with the top of your fins), then it breathes totally fine (again, disclaimer that this is the only unit I have real experience with). My understanding is that this is an effect of having back mount counter lungs and, so, a common attribute of many (most? all?) CCRs with BMCL - not special to the rEvo.
- I've heard many times that rEvo parts are expensive. I assume that means relative to what corresponding parts cost for other units. I haven't bought parts for other units, so I don't really know. I've bought almost every replacement part you can get for a rEvo, at one time or another. That is the downside of buying 10 year old, well-used/abused units. I thought they were expensive. But, I haven't had to buy anything more than once. So, if the parts last 10 years+, the cost doesn't seem that bad.

It is very popular to knock the rEvo here on SB. But, I observe that there are a fair number of people doing big dives on rEvo. I would like to know if any of you that knock that rEvo can refer me to any reports of fatalities on a rEvo that could be attributed to its lack of ability to de-water? What about fatalities due to CO2 hits?

My gut feeling is that the knocks on the rEvo are more theoretical and not based on real-world data. And that the rEvo scrubber design is so superior to other designs that it alone makes the rEvo worth serious consideration.

That said, I recognize that I am a relative neophyte in CCR diving, so my question about real-world support (meaning data) for concern about an ability to de-water is genuine. I am sincere in asking for those references. If they are out there, I'd like to learn more about what happened.

* because of the CMF, the rEvo O2 reg is set with a non-depth compensating intermediate pressure. As such, you can't dive it below somewhere around 280-300 feet (depending on specific unit's O2 reg IP) without doing "something". To go deeper, you have multiple options. You can easily convert the O2 reg back to a depth-compensating IP setup and plug the CMF. That will mean manually injecting O2 more often or the solenoid firing a lot more often. I.e. make it just like a Meg or JJ or X or any other electronic unit. OR, what I will do (haven't been past that limit yet) is plug in offboard O2 to the MAV and use the 3rd button to inject O2 into the loop during the portion of the dive that is deeper than 280. Basically, flying the unit manually during the really deep part. Once you ascend back to 280 (or whatever) and higher, the onboard O2 and solenoid start working again without having to do anything.

 

[Dsix36]

the revo can dive in eccr mode to eliminate the depth limit too.

 

[Dsix36]

I may have missed it but I have not seen a single mention of diving a eccr with a needle valve. I happen to have a Defender that is set up that way and getting ready to list it for sale. Eccr but run it manually with the needle valve and using the solenoid as a backup (parachute) works great and mitigates several failure possibilities.

You can't go wrong with James Draker. I did a try dive on a SF2 with him. He was so straight forward with both the positive and negative aspects of the unit that I had to ask him if he actually wanted to make a sale or not. His reply was simple and I liked it "I would rather you get exactly what you expected rather than buy one and end up being unhappy with it later".

 

[rvojr]

I'm a new OC not a CCR diver, but have seen some Hollis Prism 2 around the northeast. Is there any reason it hasn't been mentioned? I'm trying to learn and these posts are very informative.

 

[Compressor]

Very informative post.
Simple question: What is the most simple/reliable unit for basic recreational diving?

 

[Valyngar]

Very informative post.
Simple question: What is the most simple/reliable unit for basic recreational diving?

Jj ccr, never hear them breaking. Revos always have some leak/flooding issues.

 

[tbone1004]

I'm a new OC not a CCR diver, but have seen some Hollis Prism 2 around the northeast. Is there any reason it hasn't been mentioned? I'm trying to learn and these posts are very informative.

because it's not a good unit.... You see a lot of them because of marketing campaigns but they're not terribly well built and tend to have a lot of mechanical issues.

Very informative post.
Simple question: What is the most simple/reliable unit for basic recreational diving?

Open circuit.... The Type R units as allowed by PADI for recreational diving are anything but simple and frankly all that reliable because they have so many baby monitors on them *Poseidon, Hollis Explorer, etc.* to qualify for type R status. Even the Type T units that are considered very reliable aren't terrible simple, and the more simple you make the units, the more babysitters you cut out which makes them inherently more reliable given the lack of "stuff" to fail, but less suited for basic recreational diving.

 

[rsingler]

Very informative post.
Simple question: What is the most simple/reliable unit for basic recreational diving?

What @tbone1004 said is right. A "recreational CCR" isn't a simpler junior version. Another vote for JJ.
The build is logical. The components are solid. It's Shearwater. Lots of Delrin instead of plastic. Work Of Breathing is excellent.
But quite simply, as an eCCR, there is a workload reduction. There's not a reduction in obligation to monitor your PO2, but the toy handles it effortlessly.
The rig is known to be "heavy." Frankly, it's no worse than carrying a steel 100. In a 5mm wetsuit, I carry 4#.
But no CCR is simple. It's not like strapping on a single tank and jumping in. Maybe more like kitting up for doubles and adding an AL40. But running the checklist and prebreathe is a lot less of a big deal than I thought it was going to be.
And just noodling along on a rec dive? It's glorious on CCR. The fish don't seem to know you're there. A completely different dive experience.