[nick]

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Hi Guys,

I dive with a manifoled twin set. As a newbie I was taught to open the taps on tanks fully then close half a turn.

When doing shut-downs with a twin set it would be far quicker to just have valves a couple of turns open. At the moment I just have the isolator valve open half a turn to bleed air between the tanks, allowing me to isolate quickly. Can anyone see any problems with only having the tank valves partly open as it doesn't seem to affect my regulator's preformance even at relitively large depths (40-50m)?

Cheers,

Nick

 

[Dominic]

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You've got to be certain you know which way you're turning them - otherwise you might try to solve a freeflow by fully opening your valves.

I have my two main valves wide open, but the isolation valve only open a half turn

 

[Davey Willo]

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All valves wide open, then theres no mistaking which way they need to be turned.

 

[gaz]

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Nick,

Like Dominic says, the valves should be fine open all the way and they are designed to work like that and it makes it a lot eaiser to shut them down from being fully opened as you can't inadvently open them more. it's only very old valves that benefit from the half a turn back.

One thing to be careful with is having 'normal' style signle tank divers doing buddy checks with you when you're twinned up as some of them have a tendancy to 'check' your air supply by turning off and then the 'full on - half a tunr' which isn't what you want.

 

[Mark Chase]

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I am in the fulley open but cracked back school of thaught. I found that the fully open valve would some times be dificult to switch off if I didnt crack it back a bit on the boat. I can turn it the wrong way but only half a turn

 so whats the problem.

I have the central isolator two turns on. This allowes for quick shut downs and again if id did turn it the wrong way I would know after two turns but I dont turn that one the wrong way its only the piller valves that can get confusing in a strefull moment.

If you only have the piller valves turned on a bit you can get increased breathig resistance on the reg or no air at all after the initial tank presure drops off so thats not a good idea.

ATB

Mark Chase

 

[Rupert Bear]

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The idea for having a valve open bar a half turn is so that you cannot get confused on whether it is open or not. Having the valve fully open means that, if tight, you can never be completely sure whether it is jammed open or shut and there is a possibility of trying to force a fully open/closed valve even further open/closed. By having them half a turn closed you cannot ever get confused, if you turn it the "wrong" way in half a turn you cannot turn it anymore, you then correct your direction and close the valve. The age of the valve is nothing to do with it.
The "normal" way of operating the valves is both pillar valves open fully (apart from the slight turn closed) and the manifold valve only half a turn open. This is enough to keep the cylinders balanced but can be shut in a second or so if needed. Closing the main valves means a high risk of reduced performance from your regs as you breathe.

 

[Digger]

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I was under the impression that the old pillar-type valves had a tendency to stick open when they were cracked all the way back. Personally, I leave mine all the way open and just a crack closed. Similar reasons to what's been given, and some of my tanks still have the old pillar valves on them, so I'm sticking with what I was taught to do with them.