isolator open or closed?

[dennisgrimm]

From the teaching that has been bestowed upon me by my LDS and instructors I now dive with my isolator closed and with 2 SPG's. The reasoning for this is that in the event of a catastrophic gas loss I would not lose all of my gas. The downside is a little more gas management and thinking. So here are my questions...

How many people out there think the same way? If not, why? I get the impression that most people dive with their isolator open. Is that the case?

If you dive with your isolator open (and presumably have one SPG) and have a gas loss then you have to reach back and close your isolator very quickly to prevent a total loss of breathing gas. I think that this would be very stressful (more so than having the isolator closed). If in this scenario you have now successfully shut down your isolator to preserve as much gas as possible and are now possibly breathing from the tank without the SPG how do you know how much gas you have? Obviously you would abort the dive, but I would be worried about having enough gas to complete my deco. I realize that you could shut down the free flowing tank and re-open the isolator, but what if you weren't quick enough (because you had to shut your isolator and then your leaking tank) and lost all the gas out of that tank. Would you still re-open the isolator? Also, wouldn't you worry a little about the unlikely event where you have a gas loss in a confined place where you couldn't reach your isolator (cave or wreck)?

I have been taught that by having the isolator closed and essentially diving independents you get all of the redundancy associated with doubles without the downsides of having a manifold. In the event of a gas loss I could switch regs (if necessary), calmly (because I know that the gas I am breathing is not at risk) reach back and shut down the offending tank, check to see if any gas remains in that tank, and open the isolator if there is sufficient gas to warrant it.

BTW: I did search this topic and found a great deal of interesting discussions about the benefits of independents VS manifold, but didn't come up with anything related to having the isolator open or closed. I apologize if this has already been beat to death, I am relatively new.

 

[MikeFerrara]

This is a new one for me. There are those who are convinced that independents are the way to go. They have their system down pat and the only arguments possible are the common ones and they're not going to change their mind anyway.

But...diving manifolded doubles with the isolator closed seems like it botches up both systems. IMO, you have all the disadvantages of both without the advantages of either. What I mean is, you need 2 SPG's, have more complicated gas management, have the issue of where to put the long hose and which reg to donate and if you bust open the isolator you still loose all your gas.

True with manifolded doubles you need to be quick at shutting down a valve. So? Get fast.

What kind of diving are you doing? Any overhead? Do you use a long hose? How do you rig it?

I haven't run accross any one diving this way so I can understand why you didn't find much in print about it.

 

[Don Burke]

I've run across a variation on this where the isolator is normally shut and opened from time to time to equalize the tanks. That has some merit, although I don't think I'll be doing it any time soon.

This is the first time I have heard of someone diving with the isolator shut all the time. I'm not sure I understand what the advantage of this over independent doubles is.

I practice shutting my isolator quite often and don't worry about how long it takes since I'm pretty fast.

The point about confined spaces is interesting. Perhaps shutting the isolator before crawling into a hole is something to be considered.

 

[theskull]

When gearing up for the dive, I shut my isolator, then open it app. 3 easy twists. This makes it very easy to shut if needed, but is plenty open for the air to equlize in both tanks. I also make sure that the buddy who does my bubble check know that it is in that position on purpose.

My SPG is on my left post, as is standard, but I also have a SPG transmitter on my right post for my VYTEC computer--1 hose, but 2 independent readings on what is in the tanks.

Just 1 more option for you to consider.

Happy diving,

theskull

 

[DeepScuba]

Dennis:

My thoughts are, you are trying to fix a problem that isn't there in the first place.

You yourself point out that it is more gas management task loading, as well as having another piece of equipment (SPG) to leak/break etc.

And for what??? A problem that doesn't exist. Anyone REALLY divng doubles can already reach the isolator and shut it down quickly enough. It's a mute point. It's part of the training.

I'd rethink it (again) if I were you.

The 3 problems I've seen in my life with people involving doubles (When it comes to managing the gas in both cylinders) are ALL a result of having the isolator closed, when it would have been better to have it open. (In one case, a life saver).

 

[dennisgrimm]

Everyone, please bear with me as I am new (5 months, 55 dives) to the sport.

Deep:
You are right, I should be rethinking my equipment setup. I am doing so. I will be continiously doing so. Boards like this are a great help because I can get the advice of people from all over the world that I would not normally meet.

What situations would have been better handled with an isolator open? Please help me learn so that I don't make these mistakes.

I have witnessed 2 gas losses in my short time in diving. One involved a free flowing second stage and the other involved a first stage failure. In both senarios the other diver, like me, had their manifold closed. In both senarios by the time they checked which tank was leaking (look at the 2 SPG's) and closed the offending tank (~10 sec) most of the gas had been lost from that tank (2500 to 200 PSI).

The problem I am trying to adress by having the isolator closed is the complete loss of my breathing gas. Your are right in so far as it being a problem that doesn't yet exist. I don't think that it is a moot point. If it were, we wouldn't practice shutting down our isolator. I just feel that shutting the isolator may not be fast enough. Like I said, I have seen myself how quickly gas escapes in a free flow.

Mike:
I do mostly open water diving but occasioally travel to (and penetrate) the wrecks off of Naniamo, BC.

I rig my octo on a long hose and it is bungeed on my left tank (ANDI style). In the event of an emergency I would, and have, grabbed it and donated it. I practice this situation on a regular basis.

Why would I lose my gas if I were to open the isolator? After shutting down an offending tank, if the leak stops then it wasn't the neck seal and it would be safe to open the isolator, right?

Skull:
Isn't your setup the same as having 2 SPG's?

Don:
I think that this is the best of both worlds. The manifold crowd argues with the independant crowd saying "we can equilze between our tanks." So can I. The idependant crowd argues with the manifold crowd saying "we don't have to worry about losing all of our gas in the case of gas loss and we don't mind the extra thinking." So do I. The only trade off that I see is the extra failure points associated with having a manifold and a little bit of extra thinking. I am led to believe that manifold failures are few and far between. The thinking part of diving independats is "part of the training" and is second nature after about 5 dives.

Everyone:
I am still curious...
-if you dive with one SPG, lose a tank, shut down your isolator, then shut down the leaking tank, are now breathing off of the tank without the SPG... what do you do? do you re-open the isolator? It seems that if you don't you would have no idea how much gas you have in your tank.

In defence of what I am doing right now, I am essentially diving independants. The only difference is, in the case of a gas loss I can shut down the offending tank and open the isolator (where diving unmanifolded independants I couldn't). I do practice reaching back and opening and closing the isolator (no good if you can't use it). I recognize that by having the manifold and diving independants I have introduced 3 new failure points (each end of the isolaor bar and the isolator valve itself. However, I have traded this for the ability to equilize between the 2 tanks in case I have to shut down one of the posts.

BTW: having 2 SPG's isn't all that difficult to deal with. I just connect them together. If I grab one, I have both.

Thank you everyone for your input, I have already learned a lot through this discussion. Keep 'em coming and don't be shy, I have a thick skin.

 

[Don Burke]

dennisgrimm once bubbled... Everyone, please bear with me as I am new (5 months, 55 dives) to the sport.

Deep:
You are right, I should be rethinking my equipment setup. I am doing so. I will be continiously doing so. Boards like this are a great help because I can get the advice of people from all over the world that I would not normally meet.

What situations would have been better handled with an isolator open? Please help me learn so that I don't make these mistakes.

I have witnessed 2 gas losses in my short time in diving. One involved a free flowing second stage and the other involved a first stage failure. In both senarios the other diver, like me, had their manifold closed. In both senarios by the time they checked which tank was leaking (look at the 2 SPG's) and closed the offending tank (~10 sec) most of the gas had been lost from that tank (2500 to 200 PSI).

The problem I am trying to adress by having the isolator closed is the complete loss of my breathing gas. Your are right in so far as it being a problem that doesn't yet exist. I don't think that it is a moot point. If it were, we wouldn't practice shutting down our isolator. I just feel that shutting the isolator may not be fast enough. Like I said, I have seen myself how quickly gas escapes in a free flow.

Mike:
I do mostly open water diving but occasioally travel to (and penetrate) the wrecks off of Naniamo, BC.

I rig my octo on a long hose and it is bungeed on my left tank (ANDI style). In the event of an emergency I would, and have, grabbed it and donated it. I practice this situation on a regular basis.

Why would I lose my gas if I were to open the isolator? After shutting down an offending tank, if the leak stops then it wasn't the neck seal and it would be safe to open the isolator, right?

Skull:
Isn't your setup the same as having 2 SPG's?

Don:
I think that this is the best of both worlds. The manifold crowd argues with the independant crowd saying "we can equilze between our tanks." So can I. The idependant crowd argues with the manifold crowd saying "we don't have to worry about losing all of our gas in the case of gas loss and we don't mind the extra thinking." So do I. The only trade off that I see is the extra failure points associated with having a manifold and a little bit of extra thinking. I am led to believe that manifold failures are few and far between. The thinking part of diving independats is "part of the training" and is second nature after about 5 dives.

Everyone:
I am still curious...
-if you dive with one SPG, lose a tank, shut down your isolator, then shut down the leaking tank, are now breathing off of the tank without the SPG... what do you do? do you re-open the isolator? It seems that if you don't you would have no idea how much gas you have in your tank.

In defence of what I am doing right now, I am essentially diving independants. The only difference is, in the case of a gas loss I can shut down the offending tank and open the isolator (where diving unmanifolded independants I couldn't). I do practice reaching back and opening and closing the isolator (no good if you can't use it). I recognize that by having the manifold and diving independants I have introduced 3 new failure points (each end of the isolaor bar and the isolator valve itself. However, I have traded this for the ability to equilize between the 2 tanks in case I have to shut down one of the posts.

BTW: having 2 SPG's isn't all that difficult to deal with. I just connect them together. If I grab one, I have both.

Thank you everyone for your input, I have already learned a lot through this discussion. Keep 'em coming and don't be shy, I have a thick skin.

1. The first thing I do in a gas loss situation is shut the isolator. Looking at pressure guages is a waste of time and gas in this case.

2. If I've lost the gas in one of my back tanks, the dive is thumbed. I'm taking the most direct route out and the pressure in the remaining tank isn't an issue. I can't do anything about it if it is too low anyway.

3. If you lose a tank, you've lost the use of the first stage on that side anyway.

For the time being I'll stick with an open isolator.

 

[Diver0001]

MikeFerrara once bubbled...
This is a new one for me. There are those who are convinced that independents are the way to go. They have their system down pat and the only arguments possible are the common ones and they're not going to change their mind anyway.

<snip>

I'm a bit of a neophyte in this area still but what I've heard is that old military protocol was isolator shut. You'd breathe down one tank to 1/2 then open the isolator to even them up and then close it again. I think this was repeated a few times and then the dive was over.

R..

 

[Boogie711]

You referenced having multiple SPG's.

If you lose a tank and need to shut down, your dive is over anyway. Either you make it back or you don't. If you practice proper gas management, you have enough gas to get back safely. Period.

You also referenced finding out which tank is flowing by checking both SPG's??????? I would submit that if you can only find out which tank you have a catastrophic gas loss through by checking an SPG, you have bigger issues.

 

[dennisgrimm]

Don:
1. I don't see how shutting the isolator fixes the leaking gas. Just for the sake of discussion, if you and I were to have the exact same problem at the exact same time. First, you would be closing your isolator and I would be looking at my SPG's (if it weren't obvoius which tank were leaking in which case I would be shutting down the leaking tank). Next, you would be looking at your SPG to figure out which tank was leaking (if it weren't obvious) and I would be closing the offending tank. Lastly, I have begun my ascent and you are closing the offending tank. See how I am one step ahead the whole time? This was a theoretical situation. Maybe you are faster than me, maybe lots of things. The point is, there is one less thing to do in that emergency situation. I would gladly trade having to constantly monitor 2 SPG's in exchange for having to do one more thing in an emergency.

2. Obviously, the dive would be thumbed. The amount of gas you have woud be a big factor in deciding what to do... wouldn't it? If you have just a couple hundred PSI left wouldn't you make for the surface instead of your first deco stop?

3. I know... ya lost me on this one. ???

Stick with what you are most comfortable with, it will always be safer than a "safer configuration" that you are uncomfortable with.