Dive with isolator mostly closed?

[Smache]

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?

 

[DAJ]

You need to decide what is best for you and what aligns with your overall safety plan. Some folks run them partially open while others run them wide open. Other don’t want to deal with extra possibilities so they use manifolds without an isolation valve. Personally, I run mine all the way open and then a quarter turn back. Do you run an SPG for each first stage or just one off the left post? I use a transmitter off the right and an SPG off the left.

 

[Smache]

Just the SPG on the left. (Not opposed to transmitters, just too cheap for AI)

 

[Whitrzac]

You need to decide what is best for you and what aligns with your overall safety plan. Some folks run them partially open while others run them wide open. Other don’t want to deal with extra possibilities so they use manifolds without an isolation valve. Personally, I run mine all the way open and then a quarter turn back. Do you run an SPG for each first stage or just one off the left post? I use a transmitter off the right and an SPG off the left.

Why are you turning it a quarter turn back?

 

[DAJ]

That’s how we were taught a long time ago on how to open a high pressure valve. The idea behind it is to reduce the possibility of the valve sticking in the open position after high-pressure air has entered the valve. I suppose most of us old farts do it this way.

 

[stiebs]

That’s how we were taught a long time ago on how to open a high pressure valve. The idea behind it is to reduce the possibility of the valve sticking in the open position after high-pressure air has entered the valve. I suppose most of us old farts do it this way.

You do realise that's old school thinking for ancient valves, which is not a concern with any equipment from this century?

 

[formernuke]

You do realise that's old school thinking for ancient valves, which is not a concern with any equipment from this century?

We were taught to do quarter turn back in the navy because it prevents damage to the back seat.

 

[DAJ]

You do realise that's old school thinking for ancient valves, which is not a concern with any equipment from this century?

This is from way back… in 2018

Tank Valve Stuck Open

Went diving last weekend. Woohoo! Surfaced with ~500 psi in my rented AL80 after my first dive and couldn't get the tank valve to budge. What would you do if this happened to you?

scubaboard.com

This is from DAN:

“valves are now less prone to leaking or sticking open. While the quarter-turn-back practice is still present in other industries to prevent valve damage and ensure that valves do not stick open, the dive industry is moving away from this practice because people unfortunately keep getting injured.”

Apparently, it’s no longer recommended not because it is no longer needed but rather folks are getting confused as to what is open and what is closed. Less prone indicates that it still happens.

 

[boriss]

Just the SPG on the left. (Not opposed to transmitters, just too cheap for AI)

Having a transmitter is one of the best investments I've made. So many reasons to have it, especially on doubles:
- If you isolate you know the pressure in either tank (SPG on left post, transmitter on right post)
- Warnings as a backup on your computer
- Track your SAC rate
- Review your gas usage during specific portions of a dive*
- Extremely accurate, I've sat on deco watching my SAC rate and it was easy to figure out how much time I have left on the tank (ex: 7psi/min and I have 1000psi, I know I have enough gas for over 2-hours)
- Data is useful in planning
- Easier to see pressure at any time

* As an example, I learned my gas pressure would drop significantly during a hot drop. I always blamed it on temperature changes, but it was actually the fact that I was getting ready last minute and then breathing heavy. Wouldn't have known without the data.

Anyway, you get the point. Don't be cheap. Buy it, cry about it and enjoy the dives

EDIT: Regarding isolator, I dive with mine fully open.

 

[Smache]

Is there any reason not to dive with it open but close to closed for faster shutdown? I'm not worried about it being closed unintentionally since I check my SPG frequently and would notice if it wasn't dropping.