What if you need to use some of that 500 psi contigency reserve?

[DeepSeaExplorer]

I'm guilty...

There are times when I breath my tanks down to 100 PSI, but I do not consider it unsafe in the conditions that I do it.

I can do this because they are my tanks, not someone elses. (I treat the property of others as they expect it to be treated, and I expect the same in return.)

I do not pay for a VIP because I got below 500 PSI and no one has ever given me difficulty while getting refilled. If they did, I would just remind them that a PP fill requires draining the tank completely.

I won't do this on a dive boat, even with my tanks, because I respect their rules. I am also most likely then diving with a buddy and agree that extra reserve is required.

I usually only do this when I'm solo on a shore dive. I ususally start out with doubles, sometimes a stage, and use the last 100 PSI swimming under the waves on the way back to the beach in 20ft of water. When the gauge gets to about 100, I go up. When I get to the surface, I'm buoyant with Al 80s and there's gas left to pump up the wing. There's also manual inflation if necessary, and I have two other sources of flotation, a lift bag and a dive flag float. Also, I suppose it's not relevant, but 100 PSI in doubles would be equalivent volume to 200 PSI in a single, though I realize that it may not be fully accessible due to pressure.

I've been doing this for years and I've never had a problem with water in my tanks or regs. Others have explained how water gets in the tank. I also believe that with certain combinations of temperature and humidity that it is possible to get water in your tanks by bleeding them off too quickly to dump the gas for a PP Nitrox fill. Just as condensation forms on the outside, it may be forming on the inside as well. I think this may explain why someone that takes great care and uses a quality LDS sometimes get undeserved water in their tanks. YMMV...

I would never argue that you should do it, and if you want to come up with 500 PSI, then that's what we'll do. However, when I'm by myself, I reserve my right to dive how I choose. Some may consider that "pushing the limits", but as individuals we all have different comfort levels. While I'm comfortable with what I do, maybe I would think you drive too fast...

 

[wjefferis]

The 500 psi rule is based on dive shops for the most part. Once below that the seal on your yoke/1st stage is not as air tight and finite amounts of water can enter your tank. This makes the dive shops have to conduct a viz on the tank. Now I must say that I follow the 500 psi rule as a method of ensuring that I dont encounter an out of air situation, but if I am needing it I will suck it down to 0 psi. I dive with a 19 cu ft pony bottle so my rule of thumb is to just switch to the pony at 500 psi in the event I need it to save the viz on my own tanks since I dont rent.

 

[Darnold9999]

I have breathed a tank to empty after surfacing with 400 psi or so - needed to go back down in an emergency type situation. Was VERY glad that the tank had enough air.

Got back on the boat, told the captain, who cheerfully filled the tank for the next dive. Why would water get back into the tank unless you open the reg in water? Your lungs can't provide very much negative pressure in a scuba tank.

Wish I had drained a tank once before in a non-emergency situation. Would have known what was going wrong when the reg started to get very difficult to breath - as it was I surfaced at the same time the air gave out so no harm. Figured out later that I was down to 0 psi (couldn't get to my guage to look). Still had a pony, but couldn't get to it either without dropping my camera and was very reluctant to do that until I needed to, as it would have been impossible to recover it.

Bottom line - glad there was a reserve - no hesitation at all in using it if required - and will breathe it down to 0 if needed.

The reserve I keep depends very much on the dive. If at my local shore dive site I will swim back to shore and use the tank down to 100 lbs or so and then stand up. Enough to deal with a slip and fall into the water as I walk to shore. Off a boat at an unfamiliar dive site I am happier with a larger reserve. How much will very much depend on the dive, conditions and buddy.

 

[DandyDon]

I only dive HP tanks and if I'm below 80' I'll turn the dive between 1000-750psi.

On a 100' dive I've turned at 750 and ended the dive w/ a little below 600psi. That's with a 5 minute safety stop. If I'm above 60' I'll get my tank to 300psi.

Uh this will vary some with tank size, but do you have this backwards? :11:

500 psi reserve of a 80 cf tank full @ 3,000 is 13.3 cf

500 psi of a 80 cf tank full @ 3442 is 11.6 cf

300 psi of a 80 cf tank full @ 3442 is only 7 cf

500 psi of a 100 cf tank full @ 3442 is 14.5 cf

300 psi of a 100 cf tank full @ 3442 is only 8.7 cf

The fact that it's full at 3442 rather than 3000 reduces the amount of any psi level for reserve.

 

[ClayJar]

When we're going out on the water with our LDS, everyone's always told (by the boat crew) to be back on the boat with 500 psi. (We give our own gas plan as well, tailored to the dive site, the conditions, and the divers.) The lead instructor, however, makes certain to tell everyone that if they *need* to dip into that last 500 psi, that's what it's there for!

We've heard too many stories (some first-hand) of divers having issues underwater who then race to the surface far too quickly and with no stops in order to make it back onto the boat with 500 psi in their tanks. We let them know that if they get on the boat with less than 500 psi, there will be discussion (since that would indicate a violation of the greater gas plan or an incident such as gear failure). We also make the point that figuring out what went wrong is much preferable to a DCS hit, chamber ride, or whatever else may come from trying to hide the fact that something went wrong.


As for me, when I'm observing classes on our anchored OW boat dives, I often hit the water with the first instructor. When I make it to the stop at the end of the dive, I do not immediately exit the water at the conclusion of a "standard" safety stop. Instead, I'll hover below the stern and watch for issues until everyone's out of the water. If someone drops something while exiting, I can catch it, and I can keep an extra pair of eyes on the students, just in case.

If, in the course of hovering and watching, I get to 500 psi, I do not consider that a reason to immediately ascend to the exit. I simply monitor my gas situation a bit more closely from that point until I ascend. Rarely do I cross 500 psi -- I've had dives where I haven't crossed 1500 psi -- but I'm perfectly content to breathe the tank down to even 250 psi. At that point, I'm about 10-15 feet from the surface and well over the safety stop time (perhaps by 15 minutes or more), and my gas is not being relied upon by anyone (although there is always plenty if someone is OOA and requests some for the last 15 feet).

MF, you are the best quoter here! Maybe one day you will have an original thought?

Papa_Bear, while you are welcome to your opinions as everyone else here, please remember that the board does not want threads devolving into ad hominem attacks. If you're simply careful to direct yourself to the content and not to the posters, you should get along fine, but it's not helpful to get personal. Some of us have a vastly different perspective than you, but we should all remember the tale of "Blind Men and the Elephant" before any of us start assuming that the others' perspective has no merit.

(Remember, too, that people of experience said that nitrox was voodoo gas, but with fresh perspectives and much consideration, people of experience built a new understanding.)

 

[northen diver]

Captain, thanks for the post! Let say I find this very interesting and I am amazed at the attitudes especially about ones own safety! I must say I have read here about people expecting out of air divers to be "Calm" and well trained! I think they need to learn about the story of the Scorpion and the Turtle! In real life people who are drowning panic and do really stupid things. I am a YMCA WSI and was a full time Life Guard and the Aquatics Director For The California Polytechnic University at Pomona for three years! I am here to discuss and help because I am passionate about SCUBA and every aspect of it!

BTW that's why I do the! And I know it gets a few excited! LOL I have dealt with people for many years who put form over substance and they come out here and you get to see who they are! Some just act as if the were kicked in the head once too many times! "Let a man be known by his works" heard that some place! I am here to exclaim my love for all things SCUBA!

Do I expect you to "See the Light"? No! Do I hope a small portion sinks in and makes you think? Yes! But what I hope most of all is Divers keep diving safely and new divers continue to dive and interest their friends. I want them to have confidence that it is a safe activity with basic knowledge and they can take it as fare as they want! I want them to love and enjoy the activity as much or more than I do!

For those of you who don't know what a Public Safety Diver is, find out! These people serve the community and many of them are volunteers!

Dandy, thanks! MF, you are the best quoter here! Maybe one day you will have an original thought? nd if you Guarded I am amazed your alive! Because you are WRONG!

I is a WSI also And my son is a Aquatic director and he is only 18 years old, so I dont hold the aquatic directors in the highest regards for most of them are just young kids working through college.

This is from the USLA manual:


The first step in rescuing a drowning victim is to ensure your own safety. Then bring the victim's mouth and nose above the water surface. For further treatment it is advisable to remove the victim from the water. Conscious victims may panic and thus hinder rescue efforts. Often, a victim will cling to the rescuer and try to pull himself out of the water, submerging the rescuer in the process. To avoid this, it is recommended that the rescuer approach the panicking victim with a buoyant object, or from behind, twisting the victim's arm on the back to restrict movement. If the victim pushes the rescuer under water, the rescuer should dive downwards to escape the victim.














If you would like, I can do your homework for ya and look up the YMCA and ARC standards for a rescue along with the standards of care for a rescue for these two agencies.

 

[DandyDon]

My home buddy misunderstood the Inst in Rescue class once and did take the victim down. :11: Almost had a real rescue.

 

[Teamcasa]

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A ScubaBoard Staff Message...

Lets not let this thread go astray.... If you want to discuss rescue, start a new thread. Thanks

Reminder of the topic...

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....Now, I'd like to ask for other reasons why we try to return with 500 psi - some skippers require 700 I've heard, if y'all would like to help me out here...??

Additionally, it would be beneficial to hear from divers who do intentionally breath their tanks below 500, along with why, and what if?? If you would prefer to post that anonymously, you will need to ask a Mod to do it for you, or - PM me and I will, like I did with a denture thread.

 

[The Horn]

Amazing..........

How did this 500 psi thing all get started anyway. One of those rules of thumb by someone too lazy to gas plan I guess.

Moisture will only enter a pressurized tank while filling it (forcing it in) or if the tank has less than surrounding ambiant pressure in it (vaccuum or haul the tank under water with 0 psi in it) or leave the valve open. Those dive shops with corroded tanks should be looking into some new water seperators.

Proper gas planning is all that is required.

Running a tank down below a safety margine is just stupid and creates stress in the dive that is unnecessary. Why do that to yourself. Same with diving with someone who you think is going to panic and freak.

So your buddy has an out of air situation due to an equipment failure. Donate air and thumb the dive, surface all happy.

Perhaps the guy goes into a panic because you have told him that you are not about to share "Your" air. you are then not a "buddy" but a hole in someones backside and why dive with someone like that.

Public safety diving is a completely seperate way of working under water and completely irrelevant to the 500 psi topic.

Boat operators I would think are telling you to have 500 in your tank as then you are coming back with air and not risking your life due to lack of it. It is something they have some control over where underwater you are on your own. They can tell insurance companies that they told you to be on board with 500 in your tank and you agreed you would.......you died with zero so you broke the rules.

Rule of thirds, 6 th's, gas planning, 500 psi etc......its all there as a safety guidline. Break it because you feel it necessary, you must accept results. Break it because you are not paying attention.......don't ask me to dive with you. If you use the reserve because you needed it, then that was great, your safety plan worked!

Dive dive dive

 

[MXGratefulDiver]

Well let me tell you I have been on the California Dive accident investigation board in the 70's and investigated drownings of single and buddy teams and I will tell you you are advocating the most dangerous behavior in diving! Tell me the agency that teaches what you advocating and I will contact them, because they need to be educated! I will with my experience encourage every diver hold precious their air! Anything else is criminal!

Hmmm ... well, since the whole point of diving with a buddy is to provide a safety net in the event of accident or emergency, I guess you should contact all of the agencies ... since they all teach people to dive with a buddy. I'm sure that your superior experience would be most valuable in explaining to them why donating air in an emergency isn't a safe practice.

They might even be convinced to stop teaching air sharing as part of the basic safety protocol to everyone who takes a basic Open Water class.

Honestly, I'm not quite sure how to take your posts ... but I'm quite sure I should not take them seriously ...

... Bob (Grateful Diver)