Question Rigid vs. flexible isolation manifold for open circuit doubles?

[Nick_Radov]

For open circuit tech diving with back mounted double tanks, most of us use a rigid isolation manifold with a single isolator valve in the middle. This works fine and has proven very safe and robust. Are there any potential advantages or disadvantages (beyond cost) of switching to a flexible manifold like the Nautec Explorer that has a separate isolation valve on each side? Those are commonly used with back mounted CCRs where a rigid manifold won't fit. In principle they could be used without a CCR (just plain open circuit) but I've never seen anyone do this.

With a traditional rigid isolation manifold there are theoretically ways that the center section could fail or break leading to catastrophic gas loss. So being able to isolate each tank separately could be useful. But in practice I've never heard of this actually happening, and a flexible manifold could have other disadvantages.

(And please no off-topic replies about independent doubles or side mount or inverted tanks or anything like that, I'm not interested in those approaches.)

 

[grantctobin]

Less an issue w the Nautec, but the flexible Lola ones leak He.

Lola actually sells a fixed center crossbar for their valves, thereby eliminating the leaking issue. LOLA spojka ventilů 200Bar - 171mm | DIR-SHOP diving systems but would have to ensure it fits your bands.

I like the idea and have a set of Lola equipped 7L intended for flexibility between SM and BM off a boat, but ¯\_(ツ)_/¯ and was more a proof of concept than anything else.

 

[rjack321]

A big-ish issue with the flexible manifold is the permeability of the hose to helium. So you have to shut down the cross-over valves during storage and there's a very real possibility of filling them with a closed valve or ending up with different mixes in the different tanks. It's a necessary evil when trying to backmount 50s on a CCR. But a less than ideal when there are other options, either the SS pigtail manifold on the RB80 or the traditional rigid manifold.

The rigid crossbar on a conventional manifold is one of the strongest things in scuba, from looking at it you'd think its a weak link. Then you hear stories of doubles ejecting from pickup trucks and the manifolds bend being brass but don't leak. They are strong AF

 

[ginti]

I personally hate unmounting my JJ because the tanks go each one on their own

But yeah, what @rjack321 says is the real thing. Of course, instead of forgetting to open them, you can forget to close them when storing, and if you have trimix inside... you'll just find a quite less helium-rich mix later; not pleasant. I really do not see any advantage - skip it if you can.

 

[VikingDives]

The only idea that comes to me is it might be useful for a diver with shoulder mobility problems. Otherwise it looks like it belongs with a UTD z-system.