How tight do you keep your manifold?

[elgoog]

Hi -

During a valve drill yesterday, I felt my manifold moving extremely easily. After the dive, I checked the nuts (?) on either side and they were super loose - not even finger tight. At this point, the manifold was pointing down towards my wing inflator hose elbow. When I did hand tighten, there was some movement still possible but nowhere near what it was before.

How tight are people keeping this? Is checking this part of your pre-dive? I'm thinking of adding it to make sure it's at least finger tight.

Thanks in advance,
elgoog

 

[CptTightPants21]

Some people keep it tight with a wrench (just past finger tight) and some keep it very loose.

I keep mine pretty loose. If I am doing overhead diving (cave or wreck), I want it to have some give, but that is a personal preference. I have yet to run into a situation where it being super tight or loose affected anything, although there was one time my fully-assembled standing doubles fell three feet off a picnic table and landed squarely on the valves. Zero Damage. That may have been because the isolator, but that's hardly definitive.

 

[rhwestfall]

it is a jam-nut, so just snug the locking nut with a wrench (very mild force). Never had an issue during season...

 

[cool_hardware52]

I like to keep it just tight enough that it won't move when I want it to stay put, but will move if something hits the ISO valve knob.

That's usually just snug with a short handled wrench.

Tobin

 

[Lorenzoid]

The instructor for my Doubles course advised me to keep it tight--use a wrench to tighten just past finger-tight. He said the idea of keeping it loose enough that it would yield upon contact with the overhead was once popular but has fallen out of favor (read: fallen out of favor with the GUE crowd). He said that damaging an isolator from contact with the overhead is so rare that it's not worth the hassle of trying to tighten it "just enough"--not too tight, not too loose--and potentially having it come loose and flop down when you don't expect it, as yours did. I haven't enough experience to have an opinion of my own, and in taking a GUE Doubles course I figured I was paying good money for the collective wisdom of a bunch of experienced divers, so that's what I'm sticking with.

 

[elgoog]

Thanks for the quick replies.

Honestly, it was not this loose when I did the doubles primer and I remember the instructor checking it and saying it looked good. I did a bunch of valve drills then and all of them had me fumbling around and bumping the knob at the back of my head before I got a grip on it and was able to manipulate it. I never had it move this much then. Also, I haven't been touching the isolator while moving the tanks around so not entirely sure what loosened it up in the first place. Either way, I'm going to snug with a wrench during my rig setup the night before and also check the jam nuts pre-dive to make sure they are at least finger tight.

Another question - does moving the manifold around when pressurized impact it or the o-rings inside in a negative way?

 

[Lorenzoid]

Sounds like it just worked its way loose over time since your Doubles primer. I check mine every time I gear up to make sure the nuts are at least finger tight. Same with hose connections.

 

[Caveeagle]

Thanks for the quick replies.
Another question - does moving the manifold around when pressurized impact it or the o-rings inside in a negative way?

As long as the Surfaces and O-rings are clean and still have a little lube on them, a little rotation should not be a problem at all. If I was diving a manifold in Salt water, I would probably give them a good soak in warm water afterwards. It would take more than a quick rinse to get all the salt out of these areas.

 

[barth]

I don't use the nuts at my isolator at one set doubles. At my other two sets of doubles the nuts are just decoration.

 

[cool_hardware52]

Thanks for the quick replies.

Honestly, it was not this loose when I did the doubles primer and I remember the instructor checking it and saying it looked good. I did a bunch of valve drills then and all of them had me fumbling around and bumping the knob at the back of my head before I got a grip on it and was able to manipulate it. I never had it move this much then. Also, I haven't been touching the isolator while moving the tanks around so not entirely sure what loosened it up in the first place. Either way, I'm going to snug with a wrench during my rig setup the night before and also check the jam nuts pre-dive to make sure they are at least finger tight.

Another question - does moving the manifold around when pressurized impact it or the o-rings inside in a negative way?

I had occasion to design and build rigid extensions for ISO style manifolds, essentially a bar with a male and female end that screwed onto the iso bar to increase the Center to Center spacing for a Rebreather Application. I had to reverse engineer the design, and as part of this project I called Thermo.

They told me two things:

1) So called adjustable manifolds aren't really adjustable for C to C, they only adjustability is to allow both valves to face in the same direction, and the Iso valve to be adjusted for orientation. If one alters the center to center more than about 1 turn on either side the inner barrel oring is "unported" or no longer functional, it is no longer contacting the ID of the modular valve.

2) The purpose the dual orings is provide one oring that seals the gas (the outer ring, the one closest to the modular valve, and the inner oring which is to keep water from reaching the outer oring....

Properly employed the gas seal ring should easily tolerate slow speed rotation.

Tobin