2nd Stage regulators for Doubles

[adm3745]

Hello,

I'm starting to plan ahead for my Intro to Cave course in the fall and as such I'm investing in some new equipment to get used to before I enter the course. I just bought a new LP 108 with an H valve, and will eventually upgrade to doubles. I will have mk25's on both posts, but I'm wondering what kind of 2nd stages to use. I'm using an S600 as a primary, but am wondering what to get for a backup. My instructor recomends that I get an unbalanced 2nd stage like the R295 and I agree with this. Other people have told me that they are diving S600's on both. Does DIR reccomend the use of a simpler backup reg that is less likely to fail like the R295? Does it matter at all? Do the same concepts apply for the 1st stages...Would I be better off with a Mk2 on the 2nd post because it is almost gauranteed to never fail? Thanks for the input.

Adam

 

[Anti-Hero]

I use the S600 as the primary, and the R295 as my secondary. There is some noticeable difference in how they breathe but it's not enough to make me switch to a high-performance secondary.

 

[DA Aquamaster]

You need to consider that when things go south and you are donating gas, you will be the one on your back up reg.

A Mk 2 first stage may not deliver enough gas at depth and the hose routing is horrible.

AFAIK DIR does not currently take a position on one side of the balanced versus unbalanced argument - they just want you to use a quality reg for both primary and backup. In any event the potential for a balanced reg to fail is incredibly remote.

So one side of the argument is that you give up some performance for a statistically non existant increase in reliability.

The other side of the argument is that the minimal increase in reliability is worth the noticeable loss in performance on the reg you end up using in an emergency. Go figure.

The reality is though that you'll do what your instructor wants and use what he suggests then make your own decision later.

 

[Belmont]

Keep things simple. I use two MK25's and two S600's. I do a rotation and run them equally in both positions. The knob from the one around my neck is turned down to prevent free flow and it can be "turned up" if needed.

 

[SandyRobinson]

FWIW, my three buddies all use a MK 25 with a combination of a 600, 550, or 250 second stage. I use a MK 2/295 for a deco reg, and I can tell a definite difference in it and my buddies MK 25/600 when performing an S-drill. The 600 breathes noticeably better.

 

[adm3745]

Thanks everyone...I was deciding on the notion that the R295 was substantially less likely to fail..I'll definately go with the Mk25, because it supplies enough air for 2 divers, and I supose on 2nd thought...Being a couple thousand feet in a cave and having to swim out, I would want the easier breathing Reg.

 

[DIR-Atlanta]

You want the two second stages to be roughly equal in performance. In your cave class, you will probably spend as much time on your backup as your primary, so I would go ahead and get something comparable to the S600 you are using now. If you think the S600 is too complicated, then you might consider the S555, which is roughly equivalent (but without the dial-a-death) and uses the same parts kit as the S600.

FWIW, I currently use Mk25 firsts for almost everything, and recently upgraded some older stage regs by replacing G200B seconds with S555s. I've been very happy with the performance thus far.

 

[ScubaDocER]

The pragmatic concept of having to rely on your back up cannot be understated. I am not sure why divers want to sacrifice reliability for cost when it comes to your comfort in breathing. If you find yourself having to donate air in an OOA situation and are on your back up, you will want to breathe as easily on it as you did your primary. If you are multitasking in said OOA situation, then you will want the reg in your mouth to breathe as easily as possible. I have Apeks regs for my primary and back up and they breathe beautifully for me. Your breathing reg is the last place you want to compromise ease and comfort of breathing especially if you find yourself in a stressful situation.

 

[rjack321]

Thanks everyone...I was deciding on the notion that the R295 was substantially less likely to fail..I'll definately go with the Mk25, because it supplies enough air for 2 divers, and I supose on 2nd thought...Being a couple thousand feet in a cave and having to swim out, I would want the easier breathing Reg.

Its not less likely to fail but will breath a bit worse. I have a r380 and honestly its not a big deal. Down to 100ft it breaths fine on nitrox. At deeper depths even the worst performing regs seem just fine with trimix. I probably wouldn't use my mk2/r190 deco reg on a 190ft bottle but otherwise I wouldn't get too wrapped up in reg selection. If you are sticking with the sccubapro line, the mk10/20/25 route very nice and the s600, g250, s555 and even the r190 are all fine 2nd stages.

 

[liuk3]

FWIW, I currently use Mk25 firsts for almost everything, and recently upgraded some older stage regs by replacing G200B seconds with S555s. I've been very happy with the performance thus far.

Are you using MK25s also for all our stage and deco bottles as well? Just curious.