independent double tanks or isolator valve doubles.

[wedivebc]

The best gas management approach with independent doubles is to breathe the first tank down 1/3rd, then switch to the second tank and breathe it down 2/3rds, before switching back to the first tank for the 2nd 3rd. This leaves 1/3rd in each tank as a reserve.

This management plan uses 1/3rd of each tank on the way in, and 1/3rd of each tank on the way out. More importantly, since you only used 1/3rd of each tank on the way in, you have 2/3rds in either tank to get you back out and it ensures you will have enough gas in either tank at any point in the dive to get you back to the surface or your first deco gas in the event you lose access to the contents of either tank.

This approach also requires only 2 regulator switches and very little math (switch at 2000 on the first tank, 1000 psi on the second with 3000's).

With a set of travel bands you can use single rental tanks no matter where you travel.

Another advantage is that the tanks are fully indpendent and there is no absolute requirement to close a tank or isolator valve to prevent losing all your gas as could happen with manifolded doubles. It's still a good idea, but it's not an absolute neccesity.

I prefer a left handed valve on the left hand tank, but when traveling, turning the left tank backwards accomplishes the same thing if you cannot reach a right handed valve on your left tank.

The major downside is the heat you take from divers who are apparently overloaded by the requirement to make 2 regulator switches during the dive and to monitor another SPG.

I agree with everything DA said except the major downside part. I welcome the critisism as an opportunity to educate the drones and kool-aid drinkers. It allows me to quickly evaluate a potential dive buddy as well

 

[boogeywoogey]

Of course, there are various arguments.

The whole point of the manifold isolator is to stop some of the concerns above.

However, some of the other concerns were the splitting and walking away.

My observation is to have:

1. 2 sets of dedicated twin cylinders (all clean to 40%) one 2 x 12 litre and 2 x 10 litre

2. At least one set of singles for two nitrox double up using Buddy twiing bands...you can take em any where and impress the cobblers out of your mum, dad girlfriend.

But do the take the twin can bands anywhere......you can create a twin set immediately...YOU just need the exra first stage.


boogey

 

[Tom Yerian]

DITTO, FOR DRBILL! you can do it, but not recommended.This config. is setup as cave diving rig, for squeezes, tight entrys. Stick to back mount config. for kind of diving you describe....Capt. Tom

 

[Hoosier]

DITTO, FOR DRBILL! you can do it, but not recommended.This config. is setup as cave diving rig, for squeezes, tight entrys. Stick to back mount config. for kind of diving you describe....Capt. Tom

Capt. Tom. OK you are an expert cave diver....
But, why do every divers have to use the gear like you are using?

Have you ever heard of "eye level education"?

 

[webediving]

I am more incline to use the isolator manifold than separate tanks. I like the way the double gives me a better balanced wearing them on the back than using the side mount. I have a Dive Rite side mount set up for my Transpac BCD but I do not use it very much. Side mount is an excellent set up for cave diving but (IMHO) I find it more difucult to use in every day diving. I have a pair of OMS 112 with OMS valves and manifold. I find it easy to separate them and then adding an H-valve to use them as singles.

T