BOV with MAV and/or ADV - thoughts?

[stuartv]

Hey, Stuart...

Glad your CCR class is moving along!

I haven't used these, but I would think that the less weight on the mouthpiece, and the less you have to manipulate something that you are holding with your teeth, the better. I don't want to turn this into a BOV vs DSV discussion, but having the MAV on my chest and the ADV on a T-piece doesn't seem to be a problem that needs fixing. Both are easily accessible, neither adds much "clutter".

Unlike OC, you really don't want any water leaking into the loop via the mouthpiece - I would think that the more you are pushing buttons on it, the more likely that is to happen. A DSV is light, clean and simple.

For the BOV+ADV+MAV unit, do you really have three hoses going to the mouthpiece, or does that imply the use of dilout? Seems pretty complex.

But as I say, I haven't used anything like this, so you will probably get better advice from others who have.

Thanks!

My rEvo has the ADV inside the scrubber/counterlung assembly, so even less clutter. Having an ADV on the mouthpiece on a rEvo really seems like overkill.

But, they have a single hose adapter for the dil that you can get with this BOV (if you have MAV+ADV), so you only have 1 dil hose coming to the mouthpiece.

At this point, I will do my rEvo training with the setup it came with - no BOV at all, MAV on the chest, and ADV inside the unit. After I'm certified and get some practice time on it, then (I think) I will go for a BOV. This thread is just to give me stuff to think about on the subject as I'm going through my training and practice.

One thing I was wondering: My current MAV has a fitting and button to plug in off-board gas and be able to inject it. If I changed to this BOV+MAV setup, how would I then be able to use off-board gas? Am I going to end up still having a MAV on my chest? @Superlyte27, how are DR and DS dealing with this?

 

[Superlyte27]

There's a place to plug in off board. But, after you finish getting familiar without a BoV, and get comfortable, I doubt you'll opt for $1600 to switch to a BoV.

I don't think they're necessary. I know VERY few instructors who use them.

BTW, the ADV on the Revo is the worst I've used.

 

[doctormike]

But, they have a single hose adapter for the dil that you can get with this BOV (if you have MAV+ADV), so you only have 1 dil hose coming to the mouthpiece.

OK, so dilout only?

 

[tbone1004]

@doctormike probably easier to watch the video. You can see the splitter that allows one hose to come into the bov/dil mav for dilout, then a second hose comes over to the O2.

The issue that @kensuf brought up was water being allowed in from the O2 mav which I suspect is what caused the caustic on a friend of ours O2ptima a couple of weeks ago. I think they are in the middle of redesigning it now if not complete. Someone on here is selling one that he said Divesoft fixed, unsure what all that entails though

I agree that a year or so out when they get some more kinks ironed out it will be a no brainer vs. the Shrimp, but have to get there first.

 

[rddvet]

My rEvo has the ADV inside the scrubber/counterlung assembly, so even less clutter. H

If the ADV is in the scruber is there a way to shut it off? I've never dove a revo so have no idea.

There's a place to plug in off board. But, after you finish getting familiar without a BoV, and get comfortable, I doubt you'll opt for $1600 to switch to a BoV.

I don't think they're necessary. I know VERY few instructors who use them.

BTW, the ADV on the Revo is the worst I've used.

I'd be interested in hearing your reasons why you don't think they're necessary. A different perspective would be nice. What I've been finding is the majority of rebreather instructors that I've spoken to actually recommend a bov mainly as an additional safety factor and to promote the newbie rebreather diver to take sanity breaths if overly task loaded or unsure if all is OK. It was explained that a new diver who should probably bail out to figure out if there's an issue or not or just for sanity's sake is more likely to do it if it's just a simple switch of the bov.

Many of those instructors also either said that they don't dive bov's or that they believe bov's are great for the new diver, but eventually go to the wayside as the diver gains experience.

 

[stuartv]

My main dive buddy is over in the UK. He used to dive a JJ. Now he dives an X. He is fairly regularly diving 80+ meters to wrecks. Recently, he did a week off Malin Head, culminating with a dive on the Transylvania (129m - 420 feet).

He trained with Dave Gration (for MOD 2 and MOD 3, I believe). He trained with Mark Powell for MOD 1 (IIRC). He told me that Dave teaches all his students to use a BOV and have it plumbed straight to the dil cylinder on the back.

So, it seems that at least one pretty reputable instructor teaches BOV use not just for newbies.

My buddy uses a Shrimp on his X. I emailed him about the Divesoft and he had not seen it before, but is very interested now in checking them out.

That said, like doctormike (I think) said, I don't want this to be a DSV vs BOV thread. I just want to get any insights that y'all have regarding the Divesoft BOV and/or any BOV with an integrated MAV. Hearing about the issue that Ken and Tom are talking about is exactly the kind of thing I'd like to learn about.

 

[Superlyte27]

So, the ADV on the REVO doesn’t really need to be omitted or bypassed because it doesn’t really work that great anyway. You can just ignore it and as you get low on CL Volume, add manually. Otherwise, lots of REVO divers are just capping it off (plugging it). I vaguely remember that you could just flip the lever over and the ADV wouldn’t work that way either. I dove a rEvo for 4 years, probably 1000 hours.

On BOV’s. I’m cynical, but I believe instructors telling you that you should get a BOV is because we make a cut on the sale. So there’s that.

The reason I don’t think you need a BOV is because I think you should be so attuned to what’s going on in your loop, that if you even suspect the most minor of circumstances, you should already have bailed out to offboard gas.

I keep a long hose on my right bailout bottle. This is for my buddies. I keep a necklace on my left bailout bottle. This is for me. If my PPO2 is high or low, that’s.pretty obvious, and frankly, I’m not winded (like I might be with CO2 hit) so switching to my necklace is a piece of cake. But, when diving a rebreather, I am ultra aware of my breathing. Remember, it’s not like OC. It’s completely silent. You can hear your every breath. You can also hear your dive buddy’s every breath. By being super aware of my breathing... if it’s elevelated EVEN A LITTLE and I can’t explain it, I BAILOUT. Long before there is a catastrophic issue. Now obviously, as a beginner, you can’t diagnose what’s going on instantly. Maybe your breathing rate is elevated because you have twice as much drag as you usually carry. Or your teacher has you in a high flow environment, or you’re just stressed because it’s new toys. So what? Go ahead and bailout. It’s good practice. It’s safe. And big deal if it was nothing after all.

In my first 25 hours on the rEvo I bailed out probably 10 times. Since then I’ve bailed out once. Remember, you’ll likely have two dreams and a shearwater on your unit. But your most important computer is the brain between your shoulders. And if you use that one, there’s no need to spend the $1600 on the BOV. But, if you still want one, let me know. I’ll sell you one.

 

[Superlyte27]

There is no way I’d plumb my BOV to my DIL Cylinder on my back. Holy Crap that’s bad advice.


EDIT^
Are people really doing this?
Let’s talk about why I think that’s an absolutely horrible idea. And we’ll use your 400’+ example since you brought that guy up.

I’m at 400’ and I notice an issue, so I bailout to BOV. Now, let’s use my Optima, because it has the biggest tanks at 4liters instead of my Liberty at 3 liters (to give you the benefit of the doubt)

I’m at 13 atmosphere and notice a possible CO2 hit. I normally have a .5 sac rate, but because there’s a CO2 issue, my sac rate is triple. I’m breathing 1.5. But, I’m at 13 atmospheres... 13 x 1.5 = 19.5 cu’ for every minute. In less than 90 seconds you have drained that tank. Which is fine if the rebreather really did have a compromised scrubber. But what if nothing was wrong with the rebreather and you just has increased breathing because you got stuck, shook up by a shark, got the heeby jeebies from being down 13 atmospheres.

I’d rather not empty the DIL bottle and plumb into my bailout instead.

 

[tbone1004]

@stuartv remember that most of us here are going to be posting from a cave perspective, which usually ends up with don't plug a bov/adv into your onboard baby bottle. I'm using my onboard 3l for suit/wing inflation, many use it for a second O2 bottle.

Think about it.
Diving at 80m, 9ata. A 3l with a FULL fill has 23cf. That's less than a minute of gas if you are hypercapnic since you are also using it for your dil. That's idiotic. If you are running a bov it has to be plugged into something real.

 

[Superlyte27]

@stuartv remember that most of us here are going to be posting from a cave perspective, which usually ends up with don't plug a bov/adv into your onboard baby bottle. I'm using my onboard 3l for suit/wing inflation, many use it for a second O2 bottle.

Think about it.
Diving at 80m, 9ata. A 3l with a FULL fill has 23cf. That's less than a minute of gas if you are hypercapnic since you are also using it for your dil. That's idiotic. If you are running a bov it has to be plugged into something real.

What he said. Even if he’s in OW, the deco obligation might as well mimic a cave.