Question about diving doubles with standard reg setup.

[glen99]

I recently got a great deal on my local CL on a pair of lp95's with a non isolating manifold. The guy at the local dive shop said that I could dive with my regular singles reg setup and leave the second valve uncovered as long as I did not run it empty and did not open the second valve (obviously). In other words run my primary and secondary off of the same first stage with no reg attached to the second valve. I had no real intention of diving doubles, I dive with my daughter in local quarries so this is not technical or deep diving. I just wanted to verify that this advice is legit. Should I have any concerns about not running a first and second stage off of the second valve? Also, diving doubles do you change the end the dive at 500 psi rule to end the dive at 250-300 psi because you have two tanks?

This is the setup

2 faber lp 95's
highland millworks bands
dive rite valves, set up for yolk (not sure of they are inserts or not)
non isolating manifold (not sure of brand, but the finish is the same as the valves
steel backplate
60 lb wing

Thanks

 

[wjeiii]

The guy at your local shop is not wrong, but it dose not usually make sense to do this.
1) Need BC or back plate for doubles
2) Extra weight to carry
3) could turn on uncovered post and lose breathing gas
4) would cause others to laugh (maybe this should be #1)

 

[mahjong]

I'm curious about the nonisolation manifold--can you post a picture of the setup? Sounds like modular Dive Rite tank valves with a plain crossbar (no turn knob).

If you are diving at any depth whatsoever, even 50' to 60', you will likely reach your no-decompression limit well before you get to 500 psi.

Technically, I believe you can indeed run only one first stage and leave the 2nd valve closed. You will, however, have ratched up the complexity of your rig (ie, the number of things that could at least theoretically go wrong), while foregoing the safety benefits of an isolation manifold.

Especially with less than 25 dives under your belt, I strongly recommend that you do a formal doubles training course before you go anywhere near the water with double LP95s (or any other doubles rig for that matter). Those are big fat heavy tanks (I dive single LP95s)--you should get the feel of what it's like having them on your back in a pool before entering an open water environment.

I recently got a great deal on my local CL on a pair of lp95's with a non isolating manifold. The guy at the local dive shop said that I could dive with my regular singles reg setup and leave the second valve uncovered as long as I did not run it empty and did not open the second valve (obviously). In other words run my primary and secondary off of the same first stage with no reg attached to the second valve. I had no real intention of diving doubles, I dive with my daughter in local quarries so this is not technical or deep diving. I just wanted to verify that this advice is legit. Should I have any concerns about not running a first and second stage off of the second valve? Also, diving doubles do you change the end the dive at 500 psi rule to end the dive at 250-300 psi because you have two tanks?

This is the setup

2 faber lp 95's
highland millworks bands
dive rite valves, set up for yolk (not sure of they are inserts or not)
non isolating manifold (not sure of brand, but the finish is the same as the valves
steel backplate
60 lb wing

Thanks

 

[DevonDiver]

Whilst not "wrong", the advice isn't optimal either.

Seek out a cheap 2st stage and an extra SPG... and you've got a fully functional set of indie-doubles. This'll bring lots of advantages; primarily that you'll have redundancy and surplus gas. I dive indie doubles all the time, including to teach many recreational dive courses. It's very convenient and provides a lot of options and safeguards.

Depending on your air consumption, you could still do two dives from the two tanks:

Dive 1. Breathe from the LHS tank, until you reach your reserve 50bar/500psi etc. RHS tank is for redundancy on that dive.
Dive 2. Breathe from the RHS tank, until you reach your reserve 50bar/500psi etc. LHS is for redundancy - you'll have the 'extra' reserve left from dive 1.

**That's kind what you were asking, but without the reg on the second tank, you'd lose the redundancy. This will also result in the tanks becoming 'imbalanced' as the drained tank gets more buoyant...and the untouched tank remains more negative. This can screw with your trim (and, hence, comfort) in the water.

Alternatively, you could 'balance' the tanks over 2 dives:

Dive 1. Alternate the tanks, breathing a set amount (i.e. 35bar/500psi) from each, before changing... and repeat.
Dive 2. Continue that process.

Lastly, you can utilise both tanks for single, longer/deeper dives:

Breath 1/3rd of the RHS tank. Switch to the LHS tank and breathe 1/3rd of that. Return to the RHS tank and breath that down to a minimum reserve (can be less than 50bar/500psi). You retain the remaining 2/3rds of the LHS as a contingency reserve only. This meets the requirements of 'rule of thirds'.

To configure the regs for doubles, you need:

RHS cylinder: 1x 1st stage. 1x 2nd stage. 1x SPG. (+ 1x LPI if you have a double bladder or want LPI hose redundancy).
LHS cylinder 1x 1st stage. 1x 2nd stage. 1x SPG. 1x LPI.

It works very nicely if you configure it for long (5'-7') /short (22-24") hoses for the regs... and get shorter (24") SPG hoses also.

Here's how mine looks:

 

[eelnoraa]

If you are not planning to dive deep or deco, I recommend break the double setup apart. It sounds like all you need are two plugs, <$15. Double LP95 will likely give you two recreational dives. But why carry the gas and weight you don't need on your first dive? Just swap tank in SI.

 

[DevonDiver]

If you are not planning to dive deep or deco, I recommend break the double setup apart. It sounds like all you need are two plugs, <$15. Double LP95 will likely give you two recreational dives. But why carry the gas and weight you don't need on your first dive? Just swap tank in SI.

...and then what? Go out and buy a pony?

 

[Ste Wart]

Here's how mine looks:

View attachment 114862

 

[waterpirate]

hi and welcome,
If your dive count is accurate at less than 24, this is really a premature disscussion. If you want to ditch your singles and move to doubles right now, that is a fine plan with guidance. In the continental US people dive indies for specific reasons or missions. Side mount for example. Diving back mounted doubles with out an isolation manifold, or as indies is a slipery slope for you at 24 dives.

If you want to dive doubles find a mentor that is not trying to get in your wallet to guide you and then go diving. Increaseing your dive count in doubles that are set up in a more traditional way will serve you well prior to getting more formal training.
Hope this clears the smoke a little as some seemed to be going up.
Eric

 

[glen99]

Thanks for all of the adivce. I had not thought of running the tanks independently (without a manifold). I thinks that sounds like the way to go, I like the redundancy. To answer the question about the manifold, yes it appears to be just a crossover, with no knob. I will definately be spending some time in the pool to work on weight, trim and getting comfortable with the setup.

 

[KY_BOB]

Thanks for all of the adivce. I had not thought of running the tanks independently (without a manifold). I thinks that sounds like the way to go, I like the redundancy. To answer the question about the manifold, yes it appears to be just a crossover, with no knob. I will definately be spending some time in the pool to work on weight, trim and getting comfortable with the setup.

Working on weight? I dive double 95's in a drysuit with no lead and am still over weighted, even in salt water. I just have to deal with it. Trim is a different story. Small adjustments, up or down on your plate, will make a huge difference in trim.