Teach me about free flow

[Rainer]

Yeah, also no real thermocline in the ocean (out here it's pretty much within a couple of degrees top to bottom as well, at least in the winter). When we were ice diving, it was COLDER near the surface than at depth.

 

[TSandM]

I know from experience that a freeflow empties a single tank very quickly, so whatever you do has got to be done expeditiously, but calmly.

If I were at 100 feet, I'd have a buddy with me who has enough reserves to get both of us to the surface. If there were an identifiable cause (eg. just inflated a bag, or the reg got turned upside down and started the freeflow that way, and I just can't get it stopped) I'd go on my buddy's air and shut my tank down. But that is because I practice regularly sharing air (and so do my buddies) and I am completely confident that I can share air and remain stable and quiet in the water, or control an ascent.

The risk with shutting the valve off is that you will get separated and one diver now has lost his buddy's regulator and his own gas supply has been shut down. Not many people can turn on a single tank fast enough to avoid panic. I can turn mine on and off, but it's a laborious process. I would not want to have to do it in a situation where I had been suddenly deprived of breathing gas.

If the freeflow occurred without anything untoward happening (no identifiable increased flow) then it's an awkward situation. If your buddy has the same regs you have, the increased flow is likely to make them malfunction as well. In that case, I think you initiate a faster-than-desired ascent, and hope you will be able to go on your buddy's air when your tank runs out. Even if his reg freeflows at that point, hopefully you are shallow enough that the supply will get both of you to the surface.

Of course, I wouldn't be at 100 feet in cold water in a single tank any more.

 

[Ingolf]

The bottom line is that this kind of equipment problem is perfectly manageable and should not be an emergency for an experienced diver.

but thats the problem..

it doesn't always happen to an experienced diver, so could you explain how you can tell that its about to freeflow?

 

[jbd]

:shakehead The only purpose the question could have is for future planning. Why not start by PLANNING to have appropriate regs? It won't solve the problem, but it'll help avoid it to a good degree. Silly to mention not diving at all. :shakehead

OK, start with cold water regs. As noted in this thread, that in and of itself does not guarantee that a free flow will not happen. You're at 100+ ft in 38 degree water with a single tank and the reg is free flowing. What do you do?

 

[jbd]

but thats the problem..

it doesn't always happen to an experienced diver, so could you explain how you can tell that its about to freeflow?

Ingolf,

Check the second paragraph by captndale.

 

[1_T_Submariner]

Thanks. There are thermal layers in the ocean just not with in recreational limits.

If you look at the Temp charts for Gilboa Quarry it is cold at the bottom all year which could cause a freeze up and then thaw again once you get above it.

I dove Haigh last Sunday and registerd 40-42 the entire time so I realize there is no thremocline right now. Just wanted to bring up for the benefit of those that don't dive in cold Fresh water that alot of times there is a thremocline.

Yeah, also no real thermocline in the ocean (out here it's pretty much within a couple of degrees top to bottom as well, at least in the winter). When we were ice diving, it was COLDER near the surface than at depth.

 

[Rainer]

Oh, I agree. In the summer here, you notice the temp diff in both salt and fresh water. Just much less noticeable on the dives I've done in the winter.

 

[diverdan214]

OK, start with cold water regs. As noted in this thread, that in and of itself does not guarantee that a free flow will not happen.

I've had it happen twice with pretty high quality regs (Scubapro MK-25/S600), the second time it had been de-tuned. So yes its not guarantee but it doesn't hurt.

it doesn't always happen to an experienced diver, so could you explain how you can tell that its about to freeflow?

No it doesn't, as said I've had two and I'm far from experienced. There's a few ways. You'll hear the constant hiss, its soft first then gets louder. When you exhale there's still air flowing. The most sure sign I thought was that my teeth started FREEZING (and I don't normally have sensitive teeth).

The answer for me was breathing off the free-flow as long as possible (which lasted just long enough to signal what was going on so yeah it goes fast), breathing my pony dry, then my buddies, then a buddy share while doing a normal ascent with a long safety stop. Guess I coulda done a CESA had I not had redundancy (as excited as I was I probably would have breathed my buddies air dry way before we got to the surface) but I may have been going to the hospital afterwards instead of enjoying a second dive on borrowed regs (stayed in the shallow end this time though).

 

[Steve_Dives]

I'll relate a story of someone else's (not a scubaboard member) experience on Gilboa's deep side. The buddy pair was diving single 80's and had not filed a dive plan with the shop (violating the posted rules). That also means they entered at the shallow side and swam (underwater consuming their gas) to the deep side. Down around 100 feet or so one of the guys notices he has increasing pressure in his mouth as if something (hmmm) we're trying to inflate his mouth. He later recalled seeing bubbles escaping his reg even while inhaling. So he pulls he reg out to check it. That little pressure sensation was his reg going into freeflow, and by taking it out of his mouth he removed all the back-pressure. The reg was now in full freeflow.

He turns to his buddy for aid. Fortunately the buddy was within arms length. Unfortunately the buddy removed his primary and it went into free flow. Two divers are now free flowing at 100 feet in a cold dark quarry, and nobody knows they are on the deep side. They carried no stages/ponies/etc.

The first diver frantically signals UP and begins an ascent sipping off the freeflow and freezing his mouth to the point it was painful, worse than any ice cream induced brain or tooth freeze you've ever had. He arrives on the surface probably faster than he should have. His buddy is nowhere to be seen, but there are still bubbles below. He starts to think his buddy is at the bottom already out of air and he is witnessing his friends final breaths ascending to the surface. He of course can offer no aid as his freeflowing tank is dry. He waits agonizing over the fate of his buddy and worrying that Mike (the operator of Gilboa) will kick his :mooner: :mooner: :mooner: for being in the deep side without a plan or the required equipment. By some freak chance both divers survived that dive and did not experience a DCS problem. Both found a new respect for diving that day. The guy I talked to was clearly shaken by his experience. He was in having his regs serviced.

 

[Steve_Dives]

Edit: I would like to add a question about gas planning. Do you add a specific safety margin for Temps below 40 degrees (or a specific temp)? An example might be how much more gas would you require for a 40 vs 80 degree dive to 100 feet? Redundancy?

I was taught to read the tables for a deeper dive in cold water. So that 100 foot dive in 40F water might be read for 120 or more.

Gas consumption increases in the cold, which is where I think your question lies. I don't know a rule of thumb here.

I know my first dive in 40F water won't be to 100 feet! I also hope that I will have a drysuit before I go below 60 feet in 40F water.