Lock nuts on a manifold...

[Stoo]

I recently had a couple of my twin sets in for hydro and visual. The shop was kind enough to reassemble them for me.

The first time I dove one set, I noticed that the centre piece with the isolator valve was moving. I figured I'd snug the lock nuts up finger tight and as I was doing so, I noticed that both of the nuts where actually split... as in broken. I can only speculate about how this happened, and it isn't really the point of the thread anyway. This is the first time I didn't reassemble the sets myself.

At any rate, I went back to the shop to see if I could get some replacement nuts and this led to a discussion where one the guys there mentioned that the nuts serve no purpose and in fact, in cave diving circles, it is common to leave them loose or off altogether, to allow the centre hunk of the manifold to have a bit of play. I'm not a cave diver, but this didn't seem entirely implausible. Having said that, I like things to stay put for the most part...

I haven't had any luck sourcing replacements yet, and I'm wondering if anyone KNOWS for certain that these are, in fact, unnecessary.

Thanks

 

[chrpai]

I don't dive backmount doubles or cave dive... but I know someone who does and he was also in the camp of allowing the isolator valve to be able to move by removing the lock nuts. He's a GUE diver but I don't know if this is specifically their teachings or if it's something he picked up somewhere.

Eitherway, this is a choice to be made by you. If the shop broke it, they should fix it. ( Had to choose words carefully on that one.)

 

[wedivebc]

I would think if you were to bump the isolator to a point where you couldn't reach it that would be a bad thing and would prefer to have mine locked down once I found a comfortable position for it.
It is more likely cave trainees leave it loose until they find the sweet spot but I can't see leaving them off altogether.

 

[Stoo]

I would think if you were to bump the isolator to a point where you couldn't reach it that would be a bad thing and would prefer to have mine locked down once I found a comfortable position for it.

That's a great point. I'm not in the habit of whacking my manifold off of stuff, but I do dive in chilly water, where freeze-ups aren't uncommon. My old, gimpy arm seems to be able to get to the isolator more easily then the right post and it would suck to not have it where it's supposed to be...

Chrpai, another friend who owns a Scubapro dealership is hopefully getting nuts for me. No biggie...

 

[rlynch]

You need them, Tighten them (not overly) too. You need your isolator where you can always find it. Allowing it to move increases the chance of a manifold failure if you bang it around.
Kinda suck to have to isolate and your isolator rolled all the way back where it's un reachable
The dive shop guy is making stuff up.

 

[PfcAJ]

Keep them tight. Constant movement will wear those little orings out.

A loose isolator is a bit of a dated suggestion.

 

[elan]

I keep mine lose. once you tighten the bands in some position the isolator cannot rotate much anyways. mine rotates about 60 degrees max. If you bang the isolator in locked position it will more likely damage the threads

 

[ajduplessis]

I keep them tight, why would you want movement on the barrel o-rings?? I have once before seen a manifold fail. The diver was in the camp of keep it loose, but not any more. We will never know for sure if the additional movement influenced the failure? I have my own thoughts on this and keep mine tight.

Do what works for you. At the end, you need to trust the config you choose.

One other thing. I would disasemble the manifold and recheck everything, specifically the threads on the manifold and the inside of the valves. Those nuts just dont split!!! If force was used to tighten them to the point where they splits, damage could have been transfered to the threads.

 

[wedivebc]

I keep mine lose. once you tighten the bands in some position the isolator cannot rotate much anyways. mine rotates about 60 degrees max. If you bang the isolator in locked position it will more likely damage the threads

If your manifold gets tight when you tighten the bands you have not adjusted your isolator properly and will damage the threads.

 

[elan]

You either misread or did not understand my post.

When the bands are tightened the isolator only has little play because when you rotate the manifold it will be getting either shorter or or longer. The bands will not allow it to do so as they lock the tanks in some position. On all my tanks the manifold can only rotate freely about 60 degrees max and cannot rotate further without force.

If your manifold gets tight when you tighten the bands you have not adjusted your isolator properly and will damage the threads.