back vs stage regs

[evandroairton]

Hello everybody,
I used to dive with an apeks reg, on left post, and a Poseidon on right.
By now i am thinking about using poseidons on both sides, (since i love this regs), but of diferente models, since equal regs have equal faillure points...but there is another issue i´ve been thinking about:
I use scubapros as my stage regs, and there is a lot of conversation about 2nd stages compatibility betwen stage and at least one back reg for the convenience of have a malfunction underwater, during deco, and change the stage 2nd for the back 2nd st., as a redundance for the stage bottle reg, and that would not be possible using poseidons-back, scubapro-stage, since poseidons use dedicated hoses.
But there are people who dont say like this, and use regulators independent of this fact.
anybody would like to share experiences about it?

Thanks a lot

 

[DA Aquamaster]

I think the "equal regs have equal failure points" argument is along the lines of "how many angels can you fit on the head of a pin" - it just does not matter. If you have two generally reliable regs and keep them properly maintained the odds of a failure of both of them is infintismal.

You can also look at it the other way - two different regs have twice the number of unique failure points with twice the probability of having a failure in the first place. And practically speaking in the field if you have a problem you need twice the parts and more tools to work on them

Multiengine jet aircraft for example do not use two different models of jet engine to ensure that they both won't fail. Normally if both jet engines fail on an aircraft it is not because they are the same type but rather because a common need is not met like the fuel or oil supply.

The only environmental condition I could think of that would kill both regs in a scuba situation wouldl be extremely cold water and in that case you are better off selecting the best available cold water reg for both posts.

You are exactly right that trying to mix some models of poseiden first stages that operate at IP's in the 175-190 psi range with a second stage designed to work in the 120-145 psi range will not work.

That said, I also think it is pretty dumb to plan on using a backgas reg on a stage or deco reg in the event you have a failure or even to swap second stages.

Swapping a first stage underwater guarentees flooding of both regs and may not resolve your problem if the now flooded replacement fails. It will also be guarenteed to leave you with 2 regs in need of service at the end of the dive rather than just one.

More importantly, second stage failures are rare and if they occur they are almost always freeflow failures that can be modulated with the valve on the deco bottle. So it is pretty pointless to plan on swapping second stages. There was a brief period in my diving career when I thought this idea had some merit and left my second stages finger tight. Even with religios attention to pre-dive checks I unscrewed a couple part way during dives and on a couple ocassions they uncrewed far enough to extrdue the o-ring in the LP hose - permanently damaging the o-ring - in both cases blowing out about 1/3 of its circumfrence causing a major leak.

So in short it caused far more problems than I could have ever hoped to resolve with that approach. If you do that, leave them tightened with a wrench and bring a wrench along on every dive to swap them - which is of course a wrench you will always carry and never use so it will bring absolutely nothing to the dive.

Personally, I use the same brand of reg on both back gas and deco gas to ensure I only need one dealer/brand of parts/set of tools to address any issues. I also use the same model of reg on the back gas and the stage bottle - ideally suited to those applications and a different model of reg on the deco gas that is ideally suited to the demands of that application.

The only other consideration I give to interchangeability is to set them all to operate at the same Ip so that any second stage can be mixed/match/paired with any first stage pre-dive in the event one of them goes down. That means I can carry one spare second stage and one spare first stage and have everything covered on a trip.

 

[evandroairton]

Thaks DA!!!
About swapping first satges underwater, thats a possibility i didnt think when i wrote this thread, but your argumentation whas very valid about it.
I do agrre that second stages faillures are rare, and can be modullated by valve knob oppenings, but as i said there are people who also says that you can deal with it by switching seconds... i think there is a matter of philosophy preference here, and, despite of posting this thread, i do agree with you about it, and as i´ve said, i´m just collecting opinions.
thanks again

 

[Scared Silly]

Personally, I use the same brand of reg on both back gas and deco gas to ensure I only need one dealer/brand of parts/set of tools to address any issues. I also use the same model of reg on the back gas and the stage bottle - ideally suited to those applications and a different model of reg on the deco gas that is ideally suited to the demands of that application.

The only other consideration I give to interchangeability is to set them all to operate at the same Ip so that any second stage can be mixed/match/paired with any first stage pre-dive in the event one of them goes down. That means I can carry one spare second stage and one spare first stage and have everything covered on a trip.

I am in the same camp. 5 of 6 of my regs are the same. I have one parts kit for them. The 6th is for dry suit inflation. The only difference between a couple of them is the O2 cleanliness of them.

 

[Jimmer]

I am in the same camp. 5 of 6 of my regs are the same. I have one parts kit for them. The 6th is for dry suit inflation. The only difference between a couple of them is the O2 cleanliness of them.

Same here, 6 regs, 4 are Zeagle 2 are Oceanic. I may end up getting rid of the Oceanic's and going all Zeagle when the time comes that I need all 6 for a trip. Just for the purpose of 1 set of tools, 1 set of repair parts and 100% interchangability.

Jim