Dive with isolator mostly closed?

[divezonescuba]

On top of that, NOBODY touches my valves. Even on a babysitting cattle boat when using singles (where it seems things get messed with).... If they are adjusted by someone, I'm sitting back down and resetting.... and also having an unpleasant dialogue with someone.

Same here, but unfortunately, things can happen that you might not be aware of.

I have been present in two situations, where the person on the boat in Cozumel closed the valve while launching the diver in the water on the transom. They obviously thought that the valve was closed and intended on opening it, when in reality, they were closing it. One of those situations was me. I would not be surprised if some of the boat crew in some destinations were not even divers.

The more exotic the rig, the greater the danger. I had a boat crew person attempt to attach tanks to my sidemount rig between dives and become very confused when they could not find the tank straps on the back of the rig.

 

[rob.mwpropane]

Same here, but unfortunately, things can happen that you might not be aware of.

I have been present in two situations, where the person on the boat in Cozumel closed the valve while launching the diver in the water on the transom. They obviously thought that the valve was closed and intended on opening it, when in reality, they were closing it. One of those situations was me. I would not be surprised if some of the boat crew in some destinations were not even divers.

The more exotic the rig, the greater the danger. I had a boat crew person attempt to attach tanks to my sidemount rig between dives and become very confused when they could not find the tank straps on the back of the rig.

That's why we all need stickers

 

[Tracy]

That is exactly what I was alluding to and why I included the bit about being familiar with threads. There are those of us that do not turn threads or valves backwards no matter where they are. I could see a 9 to 5 calligrapher getting confused but a machinist is going to get it right.

There is a lot to that. When I started teaching tech courses I didn't understand the tricks people use to remember which way to turn them. After doing in awhile, I help teach them tricks to understand.
As someone who grew up on a farm and worked as a mechanic for 20 years, I just open or close it, I don't think about which direction that is. Everybody comes from different backgrounds.

 

[rjack321]

I see a few threads discussing isolation manifolds and whether they're a good idea, but none on this specific topic, so here goes...

I do a lot of solo diving, some of it in caves, where a total loss of gas would be fatal. Because of this, I practice shutdowns most dives. My philosophy is that if I hear gas escaping behind my head, I close the isolator first, both to save half the gas, and so that I can use the SPG to determine which side the problem is on if necessary.

I'm considering diving with the isolator open, but close to closed so that I can shut it down more quickly if I need to. I'm not concerned with accidentally diving with the isolator fully closed since I check my SPG frequency. Are there any dangers I'm missing by doing this?

Yes. Focusing on equipment failure is something we all tend to emphasize (to excess). The risks of a manifold failure/leak are miniscule compared to the risks of a brain fart failure.