Can I route the octo to the left side instead of the right?

[Lorenzoid]

Lets say you and your wife do a 60' dive. You decide that you will each reserve 1000 psi of gas. Your wife gets down to 1000, and you have 1500. What is the harm of sharing gas until you too are down to 1000 psi? At no point in the dive is either of you below your "rock bottom" reserve. You get to practice an air share under stress-free conditions. If anything, you are enhancing your safety for future dives.

Now, since you know your wife breathes more heavily than you, why wait until you reach her reserve pressure? Why not share gas in anticipation? Say, when you have 2000 psi and she has 1600? I can't see a reasonable objection to this.

Implicit in your objection, it seems, is that sharing gas is a risky undertaking. That may be the case for some divers. All the more reason to practice it when you both have adequate gas.

Okay, that makes sense to me. I had no idea it was common practice to share air when it's not an emergency. It does seem to go against what I was taught. But then, so do many things I read on SB. Also, I can see where the sight of two divers sharing air might cause some alarm among others in a group if they are not advised beforehand that we do this.

We have practiced donating our secondaries to each other on occasion. We've even practiced buddy breathing for what it's worth.

 

[Shftrdog]

Oceanic makes a nice Octo called the Swivel that can be used any way. There is no upside down, otherwise yes you can switch it. You can put it in any of the LP ports, it wont fit into the HP port.

 

[TSandM]

When I said "early in the dive", I meant before either diver is approaching minimum gas reserve; "too long" would be maintaining the practice beyond that minimum gas reserve. "Gas planning" is, among other things, knowing what that minimum gas reserve IS and how to calculate it, and doing so before beginning the dive, so that everything can be kept kosher.

I would definitely agree that, if you are diving with a guide or group, the "responsible" people need to know you are going to do this. We had a DM completely freak in Indonesia when he saw us sharing gas, even after we showed him our gauges that indicated we both had more than 2000 psi in an Al80. We had to cease and desist before he calmed down.

 

[flots am]

Lets say you and your wife do a 60' dive. You decide that you will each reserve 1000 psi of gas. Your wife gets down to 1000, and you have 1500. What is the harm of sharing gas until you too are down to 1000 psi?

What's wrong is that if you lose one tank (failed freeflow, clogged dip tube, etc.), you now have 1000PSI on one tank to share. however due to regulator physics and SPG inaccuracies, you can't actually count on using all of it. @1000PSI, there's about 700PSI you can "count on". On an AL80, this translates to about 18CuFt of available gas.

It's up to you to figure out if 18CuFt is enough to get you and your buddy back to the surface. Depending on depth, stress level and both of your stressed RMVs, it might not be, which will leave you with two OOA divers instead of one.

From my perspective it's not worth the risk, however your Your Mileage May Vary.

flots.

 

[vladimir]

What's wrong is that if you lose one tank (failed freeflow, clogged dip tube, etc.), you now have 1000PSI on one tank to share. however due to regulator physics and SPG inaccuracies, you can't actually count on using all of it. @1000PSI, there's about 700PSI you can "count on". On an AL80, this translates to about 18CuFt of available gas.

It's up to you to figure out if 18CuFt is enough to get you and your buddy back to the surface. Depending on depth, stress level and both of your stressed RMVs, it might not be, which will leave you with two OOA divers instead of one.

From my perspective it's not worth the risk, however your Your Mileage May Vary.

flots.

How is it riskier than two buddies with identical gas usage rates breathing their tanks down to the reserve pressure simultaneously?

When you set a reserve (rock bottom), you set it to conservatively manage an ascent for both divers from one tank. You don't pick an arbitrary pressure, you calculate how much gas you will need, considering each divers SAC, an estimate of their SACs in an emergency, and the depth. Here's NWGratefulDiver's description of the process. 1000 psi in one AL80 is plenty of gas for two divers to make a safe ascent from 60'. But even if you decide that it is not, all that means is that you set a higher reserve, it doesn't change anything with regard to the question at hand.

 

[spectrum]

What's wrong is that if you lose one tank (failed freeflow, clogged dip tube, etc.), you now have 1000PSI on one tank to share. however due to regulator physics and SPG inaccuracies, you can't actually count on using all of it. @1000PSI, there's about 700PSI you can "count on". On an AL80, this translates to about 18CuFt of available gas.

It's up to you to figure out if 18CuFt is enough to get you and your buddy back to the surface. Depending on depth, stress level and both of your stressed RMVs, it might not be, which will leave you with two OOA divers instead of one.

From my perspective it's not worth the risk, however your Your Mileage May Vary.

flots.

Done right it's just balancing of resources. Everyone always has adequate back gas to handle any emergency. The objective is to not have one diver repeatedly getting out with 1500+ while the other diver exits with 500. Of that 1000 PSI available the power breather might take 600 PSI since the donor will now need the 400 to extend his/her own dive. If appropriate cylinders are an not option it's a good way to get the most of your vacation / diving investment. If you think it's dangerous then you don't understand.

Pete

 

[flots am]

How is it riskier than two buddies with identical gas usage rates breathing their tanks down to the reserve pressure simultaneously?

In an emergency, the "heavy breather" puts the donor at greater risk than if there wasn't pre-emergency sharing because the donor now has less gas.

I find the practice quite selfish and would never even consider breathing down my wife's "excess" gas, because there may come a time when she needs it.

FWIW, it turns out that 1000PSI left in either diver's tank is enough for an air sharing ascent from 60' if they skip the safety stop and nobody is too anxious. Deeper, more freaked out or any extra time on the bottom before ascending and there will be two out of air divers.

flots.

 

[Tortuga68]

What you're talking about is purely a gas planning issue and has nothing to do with gas sharing as described in the OP which, if gas planning is done properly, is a non-issue

 

[vladimir]

What you're talking about is purely a gas planning issue and has nothing to do with gas sharing as described in the OP which, if gas planning is done properly, is a non-issue

Yes, thank you.

In an emergency, the "heavy breather" puts the donor at greater risk than if there wasn't pre-emergency sharing because the donor now has less gas.

Choose whatever reserve you want. Take into account the breathing rates and whatever degree of conservatism pleases you. None of that has anything to do with the question at hand, which is sharing gas before either diver reaches their reserve pressure.

FWIW, it turns out that 1000PSI left in either diver's tank is enough for an air sharing ascent from 60' if they skip the safety stop and nobody is too anxious. Deeper, more freaked out or any extra time on the bottom before ascending and there will be two out of air divers.

It's not worth much. Again, choose your own reserve level, based on your buddy's and your gas usage rates and your depth. As your depth changes, your reserve requirements change. Of course you'd reserve more for a deeper dive; I specified 60' for a reason. For me and the buddies I dive with, 1000 psi is plenty, from 60'.

Again, that's another subject that doesn't have anything to do with this thread. But I would recommend that you read the article by Bob that I linked to; you don't seem to have a grasp on the concepts.

 

[flots am]

Again, that's another subject that doesn't have anything to do with this thread. But I would recommend that you read the article by Bob that I linked to; you don't seem to have a grasp on the concepts.

Thanks for the slap.

I have an excellent grasp of the concepts involved, which is why I make it a point to bring all the gas I need, and reserve air-sharing for cases where someone has screwed up.

flots.