New to doubles

[Adobo]

ISOLATE, then reopen the valve you shut down, and try the other.

There's only so many options...

The process I was taught to debug post/manifold failures is for the diver to take his best crack at it and then to ask his buddy to double check his work. This process doesn't work if my buddy doesn't know what a various failures look like. Or if I don't bring a buddy along.

You have a process wherein you can figure out what the failure is without your buddy's help. Good. I am not that smart. I would follow my training and ask my buddy to come double check my work.

---------- Post added November 10th, 2014 at 05:39 PM ----------

solution there is you can flip the doubles over your head and fix them, or do proper gear checks to make sure your hoses are all tightened before the dive, and a first stage can't come loose unless it is depressurized and turned. Pretty easy concept, but if you hear bubbles, you'll be able to feel any big bubbles, so feel them and turn the dive.

Flip doubles over your head. Really?

The OP is asking about tips diving doubles for the first time. And we are in the weeds about failures and flipping tanks over our heads while we are under water.

Gotta love scubaboard.

 

[Storker]

The basics are, don't muck around with valve drills (until someone who knows shows you how) and failures (until you are in appropriate class). Put on the regs, make sure the isolator and posts are open (flow check) and dive the doubles like you were diving a giant single tank. That's the basics.

Which is also the way people I know dive doubles on rec profiles.

I've got quite a few mates who dive doubles. They don't do it for the redundant gas, but for a COG closer to their body and higher tank capacity. Period. If you consider doubles just for those reasons and never plan on going tec, that's perfectly valid reasons for diving doubles, and you can even forgo the isolation valve on the manifold (not that many people I know do that, though...).

I've even got a couple of mates who happily dive double 6L or 7L 300 bars, which doesn't give you any extra capacity compared to a single 12L or 15L. They still prefer their doubles to a big-a$$ single tank, just for the balance of the rig.

 

[tbone1004]

It's a very real way to evaluate failures and the process should have been taught in their basic OW class, it's not really any more difficult in doubles than it is in singles if you do it properly and it sure makes it a heckuva lot easier to diagnose stuff when you can see it. Odds of this being required are minimal, but I have seen it done in water twice, both times were when the diver couldn't figure out which hose was bubbling and it ended up being a leak in the valve itself. We always teach various steps of diagnosis and it is never for buddy validation.
In doubles, you hear a leak, reach back and try to feel where it is, if you can feel it, shut it off. If you can't, start shutting things off one at a time, starting with the isolator and leave it closed. Shut left post off first, then if it doesn't fix it, open left post, and switch to secondary, shut right post off. If that fixes it, then open the isolator, hopefully it doesn't come back and then you make a safe exit. If you can hear the leak but it is very tiny, then you can flip the tanks over to see the bubbles and see if you can fix it, i.e. hose was loose. That is likely not going to ever happen to anyone, but like bare-tank breathing is one of those skills that doesn't hurt to know how to do if you get up a real sh!t creek.

Realistically two things tend to happen, the IP creeps because of a bad HP seat, that leads to second stage freeflows unless you dive poseidons in which case the first stage will start freeflowing. You can see that, tell what post it is on, shut it off and turn around. The next most common thing is probably a HP hose leaking, in which case you obviously know which post it is on, and you shut it off and meander out of wherever you are.

 

[Searcaigh]

When I did my IANTD advanced recreational trimix course the instructor used an air gun attached to his LP inflator hose to blow bubbles behind me next to a valve and you had to identify what valve to shut down without help from your buddy, and honestly it was not that difficult.

Once you shut down the "offending" valve, you called your buddy over to check for leaks, then in a real life situation you would abandon the dive, however the detection and shutdown should be a self sufficient exercise.

Prior to that course I had been using doubles for about a year without any training except for setting them up.

 

[Michael Guerrero]

Jesus...this stuff isn't rocket science.

I bought some LP85s, took them in the water, and got to work.

The hose routing stuff is all over the Internet, and it's really easy. The rationales are there as well.

Looking at your rig, I agree that the tanks could come down a little more, probably another bolt hole lower. My LP85s make me head heavy, like Ron said in post #3. If the bands are at the break in the neck of the tank, you drop them down a hole, and you find yourself head heavy, it basically means they're not far enough down your back. You can add a tail weight and you can also increase the length of the shoulder straps and shorten the crotch strap (thanks TSandM for posting that a million years ago and saving the day for me).

That OPV ball you have hanging off will get some howls from DIR types so you could either take it off, or you could just push it right up against the OPV and tie a knot in the cord so you can still feel it with thick gloves but there's no entanglement hazard.

Just follow the valve drill post tbone posted and practice, practice, practice. Do some s-drills with your buddy to so you get your timing and light cord management right.

If you are going to learn these on your own, which is 100% possible, a video camera is your friend. It will show you all your mistakes and you can start making tweaks.

And of course, SB is here to help you along with questions.

Congratulations on buying a great set of all-around tanks! Get out there and get to work!

 

[rhuntley]

Thanks for all the advice everyone!

Today I managed to drag my boss/tech instructor/course director/LDS owner out to a local dive site. We went over hose routing, valve drills, failures and how the manifold works (which I already knew from filling tanks, but recap is good.)

Once in the water, we did a weight check, with a 10 pound weight belt and SS BP, my weight was just right. Once we get down, I wasn't top heavy so seemed just right. We started out simple, working on skills like checking the pressure gauge, switching regs with one hand and deploying/storing the can light. After tweaking a few things, and working on hovering/back finning, we did valve drills and OOA. Then continued on to have a fun dive. Ended up being an 80 minute dive with a max depth of 92 feet, great viz until we came upon the OW divers.

Luckily, I have no trouble reaching my valves, which was my biggest concern. Underwater pictures to come

Thanks again everyone!

 

[rongoodman]

That OPV ball you have hanging off will get some howls from DIR types so you could either take it off, or you could just push it right up against the OPV and tie a knot in the cord so you can still feel it with thick gloves but there's no entanglement hazard.

The replacement OPV from DeepSeaSupply is nice, with a thick cord but no knob on the end. I have one one all my wings.

 

[decompression]

Fantastic, that looks like WhiteCliff, right? Or Porteau cove? Was the LDS owner Greg M?


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[FinnMom]

A tail weight 1-2kg can be really great for getting your nose-to-toe balance right.
Lumb Bros Vee Tail Weight -- Divers Warehouse | Scuba Diving | Snorkeling | PADI Training | Learn to dive | Learn to dive Leeds | Learn to dive Bradford


Shutdown drills: After the 1st try my shoulder ached for 3 days, next time it was sore a day, after that I could do it no sweat.
Flexibility is something you can teach your limbs, even limbs aged 40yrs and more ;-)

 

[Michael Guerrero]

I dove with tank boots on my tanks, in fresh water only, for about 60 dives. When I took the boots off, the paint had bubbled up because the Faber boots are snug against the tank and don't properly drain water. There is the potential for rust to form underneath the boots.

My recommendation would be to remove the boots, even though it's more of a pain kitting up.