Indpendant doubles????

[Rick Murchison]

What do you do when you are on your backup regulator and your buddy wants gas? Fiddle around looking for that bolt snap to unclip before donating?

Just hand off the long hose whose second stage is still right there at my right collarbone. Since I use a breakaway (bicycle innertube rubber band) to attach my clip to the reg it is a simple, straightforward maneuver with no worries, and no need to unclip.
If there were *any* delay then I'd hand off the one in my mouth, find and use the long hose myself and then switch my buddy to the long hose after things had settled down.
Of course if you're both diving independent doubles the chances of your buddy needing gas are slim and none, expecially since you'd call the dive after the *first* reg failure and already be on the way out/up
Rick

 

[Soggy]

Thanks for the explaination, Rick.

I think I'll stick with my manifolded doubles, just the same.

 

[Wildcard]

This is a quality debate and exactly what I was looking for. Thank you all very much. I think Im sold on IDs now. I don't like the simplicity of a slung tank for one simple reason. I usualy have my camera in front and it's a hand full by it's self.
Any other input?

 

[DA Aquamaster]

My biggest problem with independent doubles is donating gas to your buddy as well as losing half your gas supply no matter what the failure is. What do you do when you are on your backup regulator and your buddy wants gas? Fiddle around looking for that bolt snap to unclip before donating? Dive with two longhoses? There just doesn't seem to be a good way to handle it.

The bolt snap issues is a non issue as it is normally attached to the reg via an o-ring around the base of the mouthpiece - a sharp tug and it will come free of the o-ring.

In the event you have a reg failure and are on your backup - meaning you only now only have one functioning reg, the dive is over and you should be on the way up. Now, it's remotely possible your buddy may have a failure during that ascent and need to use his backup, but he should also be redundantly equipped and be able to use his own backup.

It's entirely possible (and good practice) to plan for a failiure, but when you get into planning multiple failures, it is not realistic and is seldom possible to accommodate them all. In practice, if each diver equips for full redundancy and plans their dive on the assumption that they will need to be self reliant, a single failure is easily handled by the diver himself and the exeedingly rare multiple failures can still be handled within the buddy group.

If multiple failures are common in your diving - your regulator maintainence program and/or your gas planning and management really sucks.

 

[waterpirate]

In regard to donating gas to your buddy, it is not an issue. if you have a buddy simply give him a reg and turn dive. If diving deep with planned deco, what buddy? I have seen manifolds fail on the boat from not being secured properly. dumb mistake for owner, but now dive is aborted due to failure.
Independant doubles make sense to me.
Eric

 

[Soggy]

If multiple failures are common in your diving - your regulator maintainence program and/or your gas planning and management really sucks.

I was talkiong about a single failure....an OOG diver while the independent diver was on the reg without the long hose. This means that where the regulator to donate is depends on what part of the dive we are in. Ultimately, I do not think independents are particularly compatible with team diving and the more likely failures will leave you with less available gas than with a manifold.

 

[DA Aquamaster]

Personally, if I am doing any kind of technical diving, I want a buddy who is smart enough to figure out what hose I am on. If he is calm, he can help himself to the long hose, if I see him coming, I'll have the long hose in my hand to give to him. If he needs a reg right now and I am on the short hose, he can still take the reg out of my mouth, I can get the long hose and then we can switch him to the long hose.

For the most part it really is not an issue. If you are paying attention to your buddy, you will notice when he encounters a problem with his reg and can adjust accordingly.

Plus if I have an OOG buddy on a techical dive, it's the last time that moron is diving with me. I come from the other wschool of thought that each diver should configure and plan to be fully independent in terms of gas/regulator related failures and should have the means to get themselves back to the surface or deco gas. A buddy is at most a backup to the backup plan and if you have to use one to access gas, you really screwed it up. There is nothing wrong with team diving, it just is not an excuse or substitution for proper redundant configuration and planning.

I do agree with you that if I have a regulator failure on indepenedent doubles, I will lose access to all the gas in one tank. However with proper gas planning and management that still is not an issue as what's left in either tank will get you back to the surface or the first deco gas switch.

I do not agree that failures are more likely. At a minimum reg failures will happen with equal frequency regardless of whether the regs are on two single posts or on a manifold. In fact, I'd argue that the regs on independent doubles are likely to be more reliable as both are used equally during each dive. One is not used more heavily than the other and one is not essentially ignored on every dive and both factors have an effect on reliability. I used to have to swap regs mid season from manifold post to post to even out the use over the season.

A tank o-ring failure or blown burst disc is also a wash as a manifold will not preserve or allow the use of that gas any more effectively than with independent doubles.

So what you have left is the potential failure of an o-ring, seal or valve in the manifold itself and if you start counting o-rings and valves, a manifold will have more than a set of independent doubles every time. So that would be more potential failure points, not less.

Plus, lets remember that when you have a manifold with an open isolator valve, you are required to close the proper post and/or isolator in the event of a failure to prevent the loss of all your gas. In a restriction, you are going to be a lot more stressed and nervous about a freeflowing reg than I am going to be. In fact in some cases, you could be really screwed.

So in the end, I think the pros and cons pretty much even out. You have potentially more gas with a manifold in the case of a reg failure (but no other failure) and with independent doubles you have less potential for failure as well as the assurance that no immediate action is required in the event of a failure to save your gas supply.

So I'll continue to dive independent doubles and hedge my bets on the potential reg failures by diving with well maintained and very reliable regulators.

 

[Rick Murchison]

So in the end, I think the pros and cons pretty much even out.

I agree. I do personally prefer manifolded doubles when they're available and easy to get to the site. But I'll dive sidemounts or independent doubles in a heartbeat if that gets me in the water easier or through the bedding plane easier. One of my most respected and experienced cave diving mentors has gone almost exclusively sidemount or independents now, so I can easily see myself going the same way eventually.
Rick

 

[Soggy]

I think you misread my post again.

My argument was that regulator failures are far more common than any sort of oring/burst disk failure. The more likely failure will leave you with less gas when diving independents vs an isolator. That's all I was saying. You are right, there is one additional and very very uncommon failure point on the isolation manifold that independent do not have.

We both understand the pros and cons, DA...this is one of those things that we'll have to disagree on. I choose to dive on well maintained valves and regulators, making the likelyhood of a catestrophic gas loss on an isolator nearly non-existent. Basically, the only things that can cause a total loss of gas on an isolation manifold is a regulator freeflow combined with a broken isolator (two failures) *or* a sudden and catestrophic seat failure in the isolator valve itself, a problem solved with regular maintenance. Oring failures on either side of the manifold are problems that the isolator valve itself solves.