Where should I start to approach the rebreather world

[Degenerate]

Do a 60m dive for 50 minutes bottom time, then do the same thing again tomorrow?

If my rMS said I was still in the top basket after the first dive (which it would), then I would dump the top basket and cycle the other one to the top. You would be dumping your whole scrubber.

Result: You would use 2 full loads of sorb. I would use 1.5 loads of sorb. Perfectly safely. While you spend 33% more on sorb.

See this is where you are wrong.
In this example I would not change sorb between the dives (I literally said so in the post you quoted, but I guess you were too busy looking at your amazing Revo to actually READ what you quoted).
I use 1 full load of sorb while you use 1,5, I spend 33% less than you do.
So, how on earth did you come to the conclusion that I would use 2 full loads of sorb?

Also really don't get the "you are driving a car without a fuel gauge" statement.
I dive an AP which has a tempstik, it might not be the most accurate way to measure how much sorb you have left but it is far from driving a car without a fuel gauge, claiming that is just ignorant and frankly, pretty embarrassing.

I'm sure the Revo is a nice unit, but that doesn't mean every other unit is worse.

 

[stuartv]

@Nico-ITA Just my opinions here:

What the people around me dive would be a factor in my decision. But, it would be a low priority factor.

The last few times I've been on boats for tech dives, it has been almost all CCR divers. 1 OC diver on the last 6 pack I was on. 2 OC divers on a boat that had 12 divers.

Of the CCRs, there were all different types. APD, rEvo, Meg, Hollis, and probably at least one that I'm forgetting. I have dived quite a bit on my rEvo with a buddy that used to have a JJ and upgraded himself to an X.

To ME, being in the water with a buddy that has the same unit as I do doesn't really matter much. The benefit of having the same unit as your buddies is more to do with out of the water. You have an issue. Do you not know how to diagnose or fix it? But maybe a buddy does because he has the same unit. Or maybe you need a spare part that you don't have. Maybe your buddy does.

If you really learn your unit well and carry adequate spares, the benefit of having buddies on the same unit is not all the big a deal.

What could be a big deal is being able to get training. It does you no good to buy a unit if you can't find an instructor that you're able to get to and get scheduled with.

I haven't run into instructors that push an agency. Though I will say I've not ever talked to a GUE CCR instructor, really. Anyway, a CCR instructor is an instructor with whatever agency (or agencies) they are an instructor for. I would not care too much about that. Generally, the manufacturer is going to dictate the standards for what must be taught on a given unit and you'll get the same basic training from any instructor for that unit. (again, GUE being a potential exception to that) So, pick a good instructor. Don't worry about the agency.

I already posted a bunch of things to rebut some of what has been said to knock the rEvo (by people none of whom are certified on a rEvo, I don't think). rEvo is very different from the canister style units like the JJ/Meg/X. Apparently, without spending some time on one, some of its benefits are not able to be fully grasped by some people.

It SEEMS, from what I read and hear people talk about, having a CO2 hit is one of the biggest risks in CCR diving. I think that the rEvo design of the scrubber virtually eliminates that concern. As long as you don't use exhausted sorb, of course. I think the rEvo scrubber design is significantly safer than any of those canister design scrubbers, for avoiding a CO2 hit. There is no O-ring you can leave out, or spacer you can leave out, that could result in bypass. There is no single container of sorb in the rEvo scrubber that could develop a channel that resulted in bypass. There is even a rumor that the rEvo has been tested with an artificial channel created in both scrubbers and it was found that the gas mixing that occurs between the 2 scrubber baskets results in even that double artificial channel yielding almost undetectable CO2 buildup for the user.

The fact that rMS also lets you use your sorb much more efficiently is another benefit, but that is a benefit of cost, not safety. Without rMS, you have to change your sorb more often, which costs more. But, the rEvo still doesn't use as much as a unit that has to replace 6 pounds because they consumed 2. You replace 3 when you have consumed 2.

The most common knock on the rEvo is that it is not flood tolerant. You should ask those critics exactly what they mean by that. As far as I know, what they mean is that, if you get water inside a rEvo, you cannot get it out again during the dive. And that is true.

But, what does it really mean for a rEvo diver? First, I must preface this with, this is my perspective as a non-cave diver. My fun dives are on wrecks. My long dives are 2 hours, so far. So, what I might find annoying at the 2 hour mark, might be a MUCH bigger deal if it continues for 4 or 6 hours. If you are aiming to eventually get to the point of doing 6 hour cave dives, then my priorities or values on all this might not be good ones for you to have. For me, I expect to be doing longer dives - maybe even 3 or 4 hours. But, being outside of a cave, if I do a 3 or 4 hour dive, it's likely to be something relatively shallow, with relatively little deco involved. Or start deep and working shallow. Deep wreck dives longer than 2 hours means you are generally doing a LOT of deco for a relatively few extra minutes on the wreck.

So, what does it really mean for a rEvo diver for the rEvo to be "not flood tolerant"?

Well, first, how are you going to get water in the loop? Mostly commonly, it will come in at the DSV, for any of a number of reasons. What happens then? It goes into the exhale counter lung. If it's the amount of water that you get from water coming in around loose lips on the DSV or having a tear in the mouthpiece, then it gets absorbed by the shammy that you ought to have in there. More water than that, or if you don't have a shammy, it's just in there, making annoying gurgling noises every time you exhale. You can have a fair amount of water in there before the next thing to worry about.

If you get a LOT of water in the exhale counter lung, then it could start to get into your sorb. If that happens, then you have 2 issues. That sorb doesn't work anymore, and it creates a caustic cocktail. Fortunately, one, it's in the exhale counter lung, where a caustic cocktail doesn't hurt you. And, two, you still have a whole separate basket of sorb that is still dry and starts to get used (assuming the WHOLE exhale basket has been rendered non-functional, which would take a LOT of water). Also, if you have rMS, it would even tell you that you are now using the second basket of sorb. If you have been totally not paying attention and don't realize you have a bunch of water in the exhale lung, you ought to be able to recognize that now!

Another thing to note about the subject of getting water in the rEvo exhale counter lung is that there is only one nut and set of O-rings that you connect and disconnect that would leak and allow that. That is where the breathing loop hose connects to the unit itself. In contrast, units like a Meg or X have twice as many hoses in the breathing loop, with the same connection to the unit, plus 2 more connections with O-rings where the 2 hoses on each side connect to their counter lungs. Many more connections and O-rings to allow leaking, as compared to the rEvo.

[continued]

 

[stuartv]

I recently started training on a Meg - because I like to learn about any CCR I can and my shop sells and teaches the Meg. What I noted during the build is that if you get water in the Meg exhale counter lung, you CAN get it out. But, that would generally only happen if the water gets in via the DSV area. If water leaks in anywhere after where exhale loop enters the exhale counter lung, then it appears to me that you cannot get that water out. For example, if you got a hole in the loop hose next to where it connects to the head, water leaking in there would go into the can and you could not get it out. Water leaking anywhere on the inhale side doesn't have a way to get it out, either, I think. Other than you inhaling it, if it's in the inhale loop hose.

So, it just feels to me like the "big" knock against the rEvo for not being able to get water out is really a much smaller thing than people make it seem like. Using the Meg as an example, there's only 1 small part of the overall system where water can get in and you can still get it back out.

Meanwhile, I put my rEvo together wrong once. And didn't pay proper attention to the signs of the problem when I went through my checklist. The result was that I ended up on a 35m deco dive with a unit that had the inhale counter lung about half full of water. A serious flood. The result: First, I couldn't really even tell. I kept thinking it SEEMED a little harder to breathe than normal. But, the difference was small enough that I was not sure. Second, when I rolled over completely on my side to look up the anchor line, that caused 2 of my sensors to get soaked in caustic cocktail. They went totally out to lunch. Fortunately, I had 5 sensors. 1 on my controller was still fine and 2 shown on my NERD were fine. The sensors didn't go out to lunch until I was already on my way up, doing deco. So, I used the good sensors to manually run my unit, keeping the ppO2 up at 1.4 - 1.6 (for faster deco) and following the deco stops my NERD was showing me (since it still was reading 2 good sensors).

What is the point? Well, first, now I have learned what my unit might feel like when flooded. In the future, I will recognize that and I would bail to OC if it were to happen again. I was lucky in that I never went into a head down trim after it flooded. The caustic liquid in my inhale counter lung would have run down the loop and into my mouth. That said, if it were the type of dive where I really NEEDED to stay on the loop, I would have the option to do so and just know that I need to avoid going head down at all.

Beyond that, the point is that, when assembled correctly, the rEvo is very resistant to flooding. More resistant, I think, than other units that have more places where they could leak. And it is very tolerant of flooding. Mine was extremely flooded in the inhale counter lung and I could barely even tell.

However, it is true that once the water is in, you can't really get it out. It is also true that if water gets in at the "normal" place for a CCR to get water in (i.e. via the DSV, one way or another) the rEvo will handle a fair amount of that just fine and with no significant danger to the diver.

So, do you want a unit that will let water in easier, but you can get it out (IF it gets in at the right part of the loop)? Or do you want a unit that is less likely to let water in, but you can't get it out (and still works fine even with a fair bit of water in it)?

With ANY unit, if you get a LOT of water in it, you're probably going to have to bail. The SF2 is highly regarded because you can totally flood it, then de-water it, then continue your dive. But, what does that really mean? I haven't had any SF2 training, so again, I could be wrong. But, my understanding of what it means is that if you take the DSV out and turn it pointing up and do your best to let water in via the DSV, THEN you can get that water out and continue diving.

Are you going to ever flood your unit that way? DSV gets knocked out of your mouth and it's going to stay out, and pointed up for long enough to flood the whole unit?

What about flooding some other way? If the inhale loop hose gets cut or torn next to where it connects to the head, are you going to be able to deal with the water that comes in and keep diving? No. If the top of your counter lung gets cut or ripped, are you going to be able to keep diving? No. There is a video showing a Meg torture test, where Leon cuts the bottom of the CL open and continues the dive. That is cool. But, the rEvo counter lungs are thoroughly protected inside the steel or titanium case. They are not going to get cut open during a dive like exposed counter lungs (like the Meg's) could. And the Meg could only continue the dive by staying in a trim that kept the top part of the CL up. Similarly, when my rEvo inhale lung was flooded, I was able to continue that dive, too, as long as I stayed flat or head up.

I think the bottom line is that ANY unit could have some catastrophic failure that results in flooding in a way the forces the diver to go to bail out to finish the dive. Or some other problem that forces the diver to bail out. CO2 channeling or bypass, for example. I would certainly love to hear of a unit that claims that none of that can ever happen.

Because any unit can have a failure that forces the diver to finish on bail out, well, that is why we always carry bail out and plan our dives accordingly. And if you are planning properly and diving to your plan, then whether the unit floods and can't be used or whether it's something else, you are trained and prepared to handle it. So, why shun a unit just because you can't get water out of it? If it's prone to flooding, that would be one thing. If flooding is a total rarity AND you are always prepared for it, if it DOES happen, then it seems like not being able to de-water it would be a relatively minor "Con" as you are evaluating units to purchase.

No unit is perfect for every diver and every dive. Not even the rEvo. I am only attempting here to more thoroughly discuss some aspects of the rEvo that get used as reasons to knock it. Mostly, I think, by people who are not even qualified to dive a rEvo. The rEvo is a good unit. So is the Meg. And the X. There are many good units out there. Hopefully, you will have a good and accurate understanding of all the pros and cons of each unit you are considering before you actually plunk down your budget to commit to one.

 

[stuartv]

My AP in stock config is also around the 30kg mark.
I've added a 6kg backplate and a Gbox so it's a little bit heavier, but still lighter than a Revo "mini" apparently
Would be interesting to know why there is such a huuuge difference in weight between them IMO, know very little about Revos as they are not especially popular here in Europe.

The Mini is physically larger than the Micro. Also, they are usually made of stainless steel, where the Micro is always titanium. However, he did say his was a Mini titanium, which IS an option.

But, also, he said that weight was including a drysuit inflation system and a can light, I think. My weight was given without either of those.

See this is where you are wrong.
In this example I would not change sorb between the dives (I literally said so in the post you quoted, but I guess you were too busy looking at your amazing Revo to actually READ what you quoted).
I use 1 full load of sorb while you use 1,5, I spend 33% less than you do.
So, how on earth did you come to the conclusion that I would use 2 full loads of sorb?

Also really don't get the "you are driving a car without a fuel gauge" statement.
I dive an AP which has a tempstik, it might not be the most accurate way to measure how much sorb you have left but it is far from driving a car without a fuel gauge, claiming that is just ignorant and frankly, pretty embarrassing.

I'm sure the Revo is a nice unit, but that doesn't mean every other unit is worse.

You are correct. My apologies. In my haste to read the whole thread, I mis-read your post. I also did not catch you are diving with a Tempstik. That analogy was addressed to the generic "you" of all the people that are diving CCR with no Tempstick or rMS.

So, let's back up and restart on sorb usage.

Yes, you can make up an example where you would use up all your sorb. So, you'd be replacing it without wasting any of it. In that case, the rEvo is the same - assuming same capacity of sorb in the scrubber, of course.

The rEvo advantage comes in when you dump your sorb knowing that you didn't use it all, because you know that you're about to do a dive where the time you have left on your old sorb is insufficient. If that never happens to you, then that is great. For you.

Bottom line: Being able to replace only 1/2 my sorb is always going to be a potential advantage. It's only not realized if you specifically choose examples where you actually use up all the sorb in your single canister, and never have to dump good sorb and re-pack because you know you didn't have enough time left on what was in there. In the real world, I think most CCR divers with a single canister do end up dumping some good sorb fairly often, because they know they need more time on their next dive than what is left in their current load.

And, even if you always dive where you never have any waste, the rEvo is safer because if you are diving where you never have any wasted sorb, then you are diving right to the point of no return. In contrast, I would cycle my baskets and if I use up all of the sorb I had leftover from yesterday, I roll right into using the sorb in the new basket. When you use up all of the sorb you had leftover from yesterday, you have nothing.

The only time the 2 are equivalent is if you compare doing single dives that are long enough to use the entire capacity of the onboard sorb. I don't know about you, but I am FAR from dives of that length.

 

[Degenerate]

I'll agree and disagree on sorb usage @stuartv, I suppose it all boils down to the dives/profiles.
Yes, when I dump my sorb there is definitely a little bit of unused sorb in there, at least I hope so because I don't plan my dives to push to the absolute limit of what the sorb can handle, after all it is cheap and not worth taking a hit to save a couple cents.
I also think that the majority of divers who use a CCR with a single scrubber design end up dumping good sorb because again, sorb is cheap and it is not worth taking a hit to save a buck or two.
Majority of my dives are in the same/similar spot and the profiles are pretty similar in terms of depth, and we'll adjust the bottom times based on things like using sorb from previous dives, diluent and if someone decided to chug a bunch of coffe before the dive and might blow a chocolate stain in his pants an hour into the dive (this guy usually does his ascents solo, never understood why people drink coffe when it makes them **** themselves).
I like to keep things simple, and to me the concept of having 5 cells and a magical way to calculate scrubber life is not something for me personally, also it would be a bad choice for someone here in Sweden as there is no support available and I doubt there is even any instructor for it.
The discussion of # of cells has been beaten to death on here already so not going to get into that, I'm happy with my 3 cells and I know how to read them, and I am sure you know how to read your 5 ones just as well.

Again, I am sure the Revo is a nice unit but I don't think I'll be seeing one here in the EU anytime soon.

 

[Wibble]

Diving two 60m dives with 50m BT would require only one 1.3kg scrubber of the two to be changed after the dive. That the equivalent of ONE normal sized scrubber which you would change after each day.

Revo uses half the scrubber than other units.

 

[grantctobin]

Diving two 60m dives with 50m BT would require only one 1.3kg scrubber of the two to be changed after the dive. That the equivalent of ONE normal sized scrubber which you would change after each day.

Revo uses half the scrubber than other units.

A 60M 50min bottom time dive on 1.2 with 50/80GF is a three hour dive. You’re suggesting people do two of these on 1.3kg of sorb?

 

[Degenerate]

Diving two 60m dives with 50m BT would require only one 1.3kg scrubber of the two to be changed after the dive. That the equivalent of ONE normal sized scrubber which you would change after each day.

Revo uses half the scrubber than other units.

Go ahead and do those two dives with just 1,3kg of sorb, I dare you.
Might be hard to post the results from a chamber but I'll wait until you come out of it.

There is absolutely no way you are doing two 60m dives with 50min BT with your Revo while only using half the sorb the rest of us would use on our not-Revo units.

 

[Wibble]

A 60M 50min bottom time dive on 1.2 with 50/80GF is a three hour dive. You’re suggesting people do two of these on 1.3kg of sorb?

Yes.

The reason for knowing this is due to the RMS (scrubber monitoring system) which shows the remaining time left. Most importantly it shows the remaining time left on the FIRST scrubber -- known as the recycle time; once that's exhausted and the reaction front's moved to the second scrubber, this is indicated too.

In all the diving I've done on my Revo, I've never changed more than one scrubber following any diving. I've elected to throw the second only after a winter layoff.

BTW I normally limit my 60m dives to 40ish mins to keep the TTS around twoish hours and within my bailout times. With a lazy shot + trapeze this could be extended with more gas availability at deco.

 

[Wibble]

Go ahead and do those two dives with just 1,3kg of sorb, I dare you.
Might be hard to post the results from a chamber but I'll wait until you come out of it.

There is absolutely no way you are doing two 60m dives with 50min BT with your Revo while only using half the sorb the rest of us would use on our not-Revo units.

For goodness sake that is every day's diving I do. Most of my dives are around 1h30 to 2h15. I rarely do two dive days, but when I do, or I get two consecutive days of 1h30, then I will run that scrubber both days/dives. Even then I've never seen the RMS say less than an hour to recycle (replace the top scrubber).

This is where it comes in to its own. Where your JJ, Meg or X-box are rule of thumb with no fuel gauge, the RMS steps in. The AP Inpiration has a TempStick which does a similar function, but the designs are very different.

BTW the Revo rule-of-thumb if not using RMS is 3 hours for the one scrubber and 3h45m if using two. Note the second's conservative. The reality is people can get double that with the RMS.

Oh, and what about Mr Cockup (I guess that's Mr Bean to those on the western Atlantic)...

• You've forgot to install the scrubber (RMS shows two red X's showing the scrubber's not installed)
• You didn't change the scrubber (RMS shows a low remaining time left -- SOP is to pre-breathe pre-jump until it shows 45mins or more on the RMS)
• You screwed up and replaced the wrong scrubber, e.g. confused the top for the bottom (RMS shows low remaining time left)
• There's a breakthough (RMS shows the second scrubber's being used and alerts you to the low remaining time left)
• You forgot to replace the O-ring (you've picked up someone else's machine; no RMS on the Petrel) - there's no O-rings

Etc.