Keeping Isolator Valve Closed

[DeepBound]

I've been thinking of diving with my isolator valve closed. This way if there is a major failure on a first stage or burst disk, and I don't respond quickly enough, at least I can only lose half my gas.

Rather than use completely independant doubles, I'd keep the isolator manifold there, so that I can open it in the case of a regulator failure.

I have a um, weirder / more original idea. Instead of swapping regs all the time, I'll just open the isolator occasionally to equalize the tank pressures.

I'd really appreciate any feedback on this. Is there anything dangerous about these ideas that I should consider?

Thanks in advance.

P.S. I'd have an SPG on both posts.

[rjack]

You are going to whack yourself by inadventently getting different mixes in those tanks!

How many times has a mix been screwed up vs. a burst disk or neck o-ring rupture. The former happens on-and-off. The latter is extremely rare.

So you are trading a rare fatal risk for a common fatal risk. Not a good deal IMO.

Keep the isolator open or go with independents if you're really scared about losing gas in these rare failures.

Richard

[DeepBound]

Keep the isolator open or go with independents if you're really scared about losing gas in these rare failures.

Thanks for the tip. Is there anywhere down in cave country that rents independent doubles?

[FW]

I dove with some Australians in Mexico. They were used to diving independents. They started the trip with the isolator fully closed. Then they went to a just barely cracked open isolator. By the end of the trip, they just left it open.

If you are really concerned about loosing all your gas, you should go sidemount, not back mounted independants. At least you can reach the valves. You can also "valve" air out of one with a freeflowing reg, which you can't do backmount.

[DeepBound]

I dove with some Australians in Mexico. They were used to diving independents. They started the trip with the isolator fully closed. Then they went to a just barely cracked open isolator. By the end of the trip, they just left it open.

If you are really concerned about loosing all your gas, you should go sidemount, not back mounted independants. At least you can reach the valves. You can also "valve" air out of one with a freeflowing reg, which you can't do backmount.

It was this thread that got me thinking of how useless an isolator valve can be if it's open:
http://cavediver.net/phpbb2/viewtopic.php?t=5243

Maybe I'll try leaving it open just a crack, like you said the Australians did, until I can get into sidemount.

[Serota]

I must be dense, but I don't get the point of leaving the isolator "barely cracked open" unless its just so you could close it faster. Is that the idea?

[DeepBound]

I must be dense, but I don't get the point of leaving the isolator "barely cracked open" unless its just so you could close it faster. Is that the idea?

When, say, the regulator explodes on your left post, and all of the air is leaking out during the 30 seconds it takes you to get your left post turned off, not much gas will have escaped from the right tank, since the isolator valve is only open a crack. If the isolator was open all the way, you could lose all the air from both tanks.

Also, yes, it'll be a bit faster to close, and less urgent to get it closed in scenarios where you need to close it.

[curtschu]

Deepbound Please see the search function I think you will find this has been discussed many times. There is being ready for a failure and then there is over thinking what could possibly go wrong!! When was the last time you heard of a regulator exploding? Now a LP hose that is another matter but you should be checking your gear. This is a situation where personal preference comes into play. you need to dive the way that make you confident in your gear. I dive a manifold. I dive with buddies if I solo I have AL I think there are others that dive independant doubles but if you are going to do that just get a Nomad or Armidilo and side mount.

[Angie Reim]

If you are really concerned about loosing all your gas, you should go sidemount, not back mounted independants. At least you can reach the valves. You can also "valve" air out of one with a freeflowing reg, which you can't do backmount.

That's why I went sidemount. I could never get past the idea that I couldn't see what was happening with my posts and isolator valve. I went SM and >90% of the paranoia pie just disappeared. I became a better diver and a better buddy for it.

[DeepBound]

I dive a manifold. I dive with buddies if I solo I have AL.

Thanks for the advice. Do you have to avoid tight spots when carrying AL, or did you get used to it enough that you can take it in the small areas?