Things Scuba Instructors teach that are either bad or just wrong.

[mdwalter]

That awful one with pineapple, who thought of that?
Let us run to 17 pages.

Edit: use to us.

Pretty sure that was somebody in Hawai'i, and it's delicious. But it is a bit strange to consider that a pizza.

 

[mcohen1021]

Like almost everyone, I learned to turn the valve back a quarter turn. When I started technical diving long ago, I was told that was nonsense and our valves should be fully opened. I complied. The problem was that when I was trying to do valve drills, I found it hard to start the valves. It took a good effort to start the turn, after which it went easily. So I don't back it off a quarter turn, but I do back it off.

Saw this debate on the boat last week. Everyone on the boat did a 1/4 turn back, the only tech diver instructor on the boat went full on, no turn back.

Is there a PADI recommendation? I havent taken or halped with a class in years, but we were taught 1/4 turn back.

Then again, in 1989, we were certified to 140 ft.

 

[boulderjohn]

Is there a PADI recommendation? I havent taken or halped with a class in years, but we were taught 1/4 turn back.

Then again, in 1989, we were certified to 140 ft.

1. PADI has no such recommendation.
2. Nothing has changed in the certification depth.130 is the official depth, with 140 in the tables as a contingency depth.

 

[BlueTrin]

Pretty sure that was somebody in Hawai'i, and it's delicious. But it is a bit strange to consider that a pizza.

Sotirios "Sam" Panopoulos was a Greek-born Canadian cook and businessman, credited as the inventor of Hawaiian pizza.

 

[Jeff_O]

Saw this debate on the boat last week. Everyone on the boat did a 1/4 turn back, the only tech diver instructor on the boat went full on, no turn back.

Is there a PADI recommendation? I havent taken or halped with a class in years, but we were taught 1/4 turn back.

Then again, in 1989, we were certified to 140 ft.

Saw a shop owner say unlearn 1/4 turn. It is on YouTube and say it was old maybe pre 80 when I learned it, tank valves could get water intrusion of the outer valve spring parts an rust. Newer valves don't need 1/4 turn back so forget it. Open fully.

 

[BRT]

A couple of years ago in Cozumel I had the dickens of a time to turn off my valve. It had stuck just like they told me it would many years ago. But I still open them all the way.

 

[johndiver999]

Saw a shop owner say unlearn 1/4 turn. It is on YouTube and say it was old maybe pre 80 when I learned it, tank valves could get water intrusion of the outer valve spring parts an rust. Newer valves don't need 1/4 turn back so forget it. Open fully.

So you think the new valves and old valves differ in their exposure of the spring to sea water? I'm not sure that aspect (or much else) has changed.

 

[BRT]

So you think the new valves and old valves differ in their exposure of the spring to sea water? I'm not sure that aspect (or much else) has changed.

I think that when a valve is sitting in the hot sun and is opened all the way, the stem is longer than it will be when it has had air flowing through it and is in the cooler water. This shrinks the stem, locking up the valve.

 

[Polarorbit]

• For the SPG issue, I had always taught students to press the faceplate facing and on the side of the tank before pressurizing SLOWLY. Maybe that was just a PADI thing.
• Pure O2 on the surface can be a great help with a hangover......!!!

Regarding the OP's question, I think that one of the worst things taught is to turn your tank valve fully on and then back 1/4 turn. This stupid rule can result in a tank being partially or "barely" on. Just open the valve or close the valve till it stops.... No need to crank on it. A tank that is barely on can be a problem. Fully on or fully off and there can be no confusion or uncertainty.

DAN supports the position that tank valves should be fully on (Old Habits Die Hard). Backing off puts them in an indeterminate state where you can't tell if they are fully open or not.

 

[Polarorbit]

That's actually to protect the hp seat in the first stage. The knife edge on the seat is small, and when 3kpsi hits, it can leave a mark. In the old days it was not too unusual to see a seat crack on first turn on. That would be before the turn of the century. The last one that popped on me was early 2000s. It certainly got my attention as the tank was on my back when the knob was turned on. Those brown stains did not come out.

Though I've never seen it, from what I understand, at high FO2, rapidly fully opening the valve can cause the valve seat to ignite. Perhaps this is the genesis of pushing the purge while opening the valve.