Scubapro Spare Air - no surprise LOA

[redacted]

All guess work on what happened. Some of my immediate thouhhts.

The latest regulator technology delivers gas down to a very low pressure without an obvious drop in performance. I know my MK25 will deliver gas at less than 20 bar and I cant tell I am low. When the critical pressure is reached you will only have 3 to 5 breath before the 1stage stops delivering gas. Not like in the old days where breathing gradually became harder. The aware diver will notice something wrong during those last couple breaths, but the distacted diver struggling/focused on drysuit management will not notice this.

The faulty gauge and lower gas pressure in conjunction with high performance regs caught the diver suddenly off gaurd in OOA. Overweight with new drysuit caused panic and all thought processes fell flat.

"The latest regulator technology delivers gas down to a very low pressure without an obvious drop in performance"

I'm interested in your comparison between "old" regs and current hi performance regs.

If I'm running *really* low on gas. I would like to know right away, not just when I have 0 - 3 breaths left.
And what we are saying is that if you are task overloaded or panicked then you've maybe only have zero breaths left when you are finally forced to face
the stark reality that you've run the gas a little bit too far.

I would prefer a much safer system of... lets have a "reserve tank"

It's not an optional "pony", it's an obligatory built-in "reserve tank" - just like on an (old) car.
When (if) you go OOA (which would be about 20 breaths earlier under my system) you just hit the big (red???) panic button and suddenly you have a couple of options again. (I.E - 20 - breaths)
Obviously you have to be able to push this button with either hand, or maybe just with you head. It has to be idiot proof since if panicked or OOA you are likely to respond in such a manner.

PS - not sure how this relates to other gas mixtures or whether it even needs to?? - probably only really usefully at shallow depths.

This discussion is getting pretty far removed from Quero's accident now but I'd like to respond to this because I have actually done a test like this. I won't bother with all of the details but the difference in how much warning you get between older regs (I used an unbalanced piston from 1972) and a modern high-performance reg is huge.

Basically my conclusion is that with an older reg, especially an unbalanced one, you get some warning as stiffness really starts to become noticeable with a bit over 10 bar left in the tank. A high-performance reg, however will give you *maybe* 2 or 3 breaths.... or in other words, about what you get with the pressure in the hoses. In the test I did the tank pressure when empty using a high-performance reg was so low that I could open up the valve and blow air back into the tank with my mouth.

In other words, there *is* virtually no warning and all this stuff about stiffness doesn't apply (in my experience) to modern regulators. Your only protection from that is to monitor your air pressure.



Before the advent of the spg tanks did have a "reserve" mode. It was a feature of the tank valve called a "J-valve". One manufacturer (I believe it may have been Dacor) also built a J-valve into one of their regulators.

If you ask me, a "reserve" mode doesn't make any sense. You need to monitor your instruments. That's the only thing that makes sense. For a reserve some divers also use a totally separate "pony" or "stage" tank but that's more for "bail-out" in case of a regulator malfunction than any part of the gas plan.



The only thing that's really useful is to monitor your gas supply and never get in that situation. Going OOA is probably the trigger for about 50% of accidents and it's the *one* thing that is completely avoidable.

R..

We already have that ... it's called gas reserves, and it's something you're supposed to learn about in your basic scuba training.

If the gauge is off by 150 psi and you run out of air, then the simple conclusion is that you're cutting your reserves too thin ... way past what your training says you should be doing ...

... Bob (Grateful Diver)

There's a reason J-valves fell out of favor ... it had less to do with the SPG than it did with how easy it was to misuse the J-valve and find yourself without any reserve at all.

Any piece of equipment is only as good as the willingness or ability of the user to use it correctly ...

... Bob (Grateful Diver)

Split from the A&I discussion.

You do not need to give up on high performance to have your regulator warn you of low air situations. The Scubapro Mk7 (Honker) will do the job quite nicely even while using a high performance 2nd. Independent of what your SPG reads, it provide an audible warning of LOA at about 400 psi. And in case you want to continue pushing it, at about 150 psi. it severely curtails air delivery to your primary (not comfortably usable), forcing you to go to your alternate with just about the amount of gas provided by a Spare Air. And it has no settings (just normal service) so it does not suffer from the drawback of a J-valve.

I started using a Mk7 as it corrects my feet heavy trim. But I also use it when I am weeding Aquarena Springs which often results in zero vis. I usually do 2 dives on my HP 100 so I am pushing my gas supply on the 2nd dive. I move out of the zero vis to check my SPG regularly so the honking has never been a surprise; but I do let it go to that level on some of my 2nd dives. And I have occasionally been forced to my alternate when I found another patch of hydrilla as I was approaching the exit.

 

[beaverdivers]

I remember the good old Scubapro MK7. It was a beauty. Why did this solution die?

 

[DevonDiver]

I remember the good old Scubapro MK7. It was a beauty. Why did this solution die?

Perhaps someone recognized a logic flaw in the concept of supplying less air in an low-on-air emergency?

:headscratch:​

 

[agilis]

I remember the good old Scubapro MK7. It was a beauty. Why did this solution die?

Because it's nearly the size of a bowling ball and remarkably heavy. Great performance, but I tend to dislike equipment that blows whistles or sirens at me.

 

[redacted]

I remember the good old Scubapro MK7. It was a beauty. Why did this solution die?

Perhaps someone recognized a logic flaw in the concept of supplying less air in an low-on-air emergency?

:headscratch:​

I suspect it died because it was quite a bit more expensive than other 1sts and offered little added value. Cost is not much of an issue on the used regulator market now.

I doubt if many folks realized what happened as tank pressure continued to fall with the Mk7. I like to test the limits of my gear but most divers do not seem to be very interested. BD - do you know if Scubapro addressed and documented that feature? I would expect they did not.

It is probably 4X the weight of other 1st stages in the 3000 psi version.

 

[halocline]

Perhaps someone recognized a logic flaw in the concept of supplying less air in an low-on-air emergency?

:headscratch:​

It doesn't deliver less air, just re-routes it to the alternate 2nd. Frankly, if you're at 150PSI and don't realize it, even with the honking, you could probably use another reminder.

I suspect the MK7 came along at a time when many divers were not using the latest and greatest dive accessory, the SPG.

 

[kelemvor]

Split from the A&I discussion.

You do not need to give up on high performance to have your regulator warn you of low air situations. The Scubapro Mk7 (Honker) will do the job quite nicely even while using a high performance 2nd. Independent of what your SPG reads, it provide an audible warning of LOA at about 400 psi. And in case you want to continue pushing it, at about 150 psi. it severely curtails air delivery to your primary (not comfortably usable), forcing you to go to your alternate with just about the amount of gas provided by a Spare Air. And it has no settings (just normal service) so it does not suffer from the drawback of a J-valve.

I started using a Mk7 as it corrects my feet heavy trim. But I also use it when I am weeding Aquarena Springs which often results in zero vis. I usually do 2 dives on my HP 100 so I am pushing my gas supply on the 2nd dive. I move out of the zero vis to check my SPG regularly so the honking has never been a surprise; but I do let it go to that level on some of my 2nd dives. And I have occasionally been forced to my alternate when I found another patch of hydrilla as I was approaching the exit.

I've got an MK7 in the other room in great shape. Got it from a friend and took it in for service. After I got it serviced, the tech mentioned it was only rated to 2200psi! I haven't used it since then.

 

[ams511]

I've got an MK7 in the other room in great shape. Got it from a friend and took it in for service. After I got it serviced, the tech mentioned it was only rated to 2200psi! I haven't used it since then.

The MK-7 came in different versions throughout the years. The latter versions have a heavier yoke. My understanding is that the 2250 psi version is fine for 3000 psi but not for a HP tank.

 

[raftingtigger]

Got my MK7 6 months after it's debut. Didn't trust a J-valve and an SPG was far more expensive than the MK-7. I still dive, as my primary, the 109A 2nd that came with it. I would still be diving the 1st except for 2 reasons. First it only has one HP port and 2 LP ports. The LP ports are both on the right side, so it is awkward to route a BC inflator hose. By the time you add swivels and blocks it gets pretty unwieldy. Second is the 2250 psi rated yoke.

When my son started to dive I got him a heavier yoked model because I wanted him to have just that little extra backup reminder for his air. He's gotten to the point where this isn't a concern of mine and he dives my back-up long-hose because it is more streamlined.

The real beauty of the honker was that it not only alerted you, but it alerted the divers around you, and personally (I tried in a pool several times) it was so obnoxious I couldn't keep diving it for more than 30 seconds before I gave up and surfaced. Since an SPG is de-rigor now, the MK7's time has passed.