Manifolds on Twins: It's an open and shut case

[Jen S]

I dive with mine half a turn open. I like it this way 'cos can just forget about it for the dive, unless the s**t hits the fan of course!
I can see the argument for closing & opening it, but like I said, I'd rather not task load throughout the dive & just let the manifold do its thing!
Jen

[Padowan]

Originally Posted by Jen S

...I can see the argument for closing & opening it...

In time, you will see the light and your vote will need to be re-cast! Another follower in the making...

[daz]

Half a turn open,

I know that there is quite a following of the "Fully closed and equalise occasionally" idea, but I would say to them....

I respect your opinion but you are wrong

Just go with whatever you prefer. I think if I had got used to diving with it fully closed and equalising often I would probably use that method but I've practised quite often and don't want to go through playing around with a new method. If it ain't broke and all that.....

Daz

[And]

Hi

Open all the way, don't go for the isolator first anyway, I go for my right post.

The reason:

Because as my wing and primary reg are on the right post it will be the one which is more likely to fail, at least in terms of freeflow. Realistically the only other failure is hitting the valves and knocking the first stage seal.

My left post has my backup reg and spg, and therefore is not working at all so it is extremely unlikely to fail

If, after closing the right post, I will isolate and my buddy will check my valves to see what is wrong. He will determine whether there is a terminal error or something that can be fixed. He also has extra gas should I need some, like if the manifold itself fails.

My isolator is fully open so there is absolutely no confusion whatsoever about which way to turn it, whether it be me or my buddy.

Andy

[Andy the Coastie]

Originally Posted by Jen S

I dive with mine half a turn open. I like it this way 'cos can just forget about it for the dive, unless the s**t hits the fan of course!
I can see the argument for closing & opening it, but like I said, I'd rather not task load throughout the dive & just let the manifold do its thing!
Jen

Digger is copying the idea ....... but the instructor failed to let him know the real reasons, so he thought he would ask a boat load of teckkie divers to make him look / feel good


opp's HI Jen

There are two good reasons for not opening and closing your manifold during a dive.
1.By equalising tanks rapidly you will find out that when you open up for test that one tank will be very rusty inside. The sudden drops in pressure cause condensation to form and failed a lot of tanks in the past when this method used to be more common.
2.One of the whole points of manifolds is the reduction in task loading, they are a single cylinder unless a fault causes a problem that requires manipulation. Opening and closing the manifold makes it fairly pointless having one, you would be just as easy using independents IMO.
There is no need to have the manifold opened any more than 1/4-1/2 turn and it takes only a second or two to close. I just can't understand the argument about keeping it open all the way in case of confusion. Never ever had a problem no matter what way wat up remembering what way to turn a tap. Even if I did if it didn't close up to the stop in one twist then it is being turned the wrong way!

[aclivity]

Originally Posted by RubberBoy

1.By equalising tanks rapidly you will find out that when you open up for test that one tank will be very rusty inside. The sudden drops in pressure cause condensation to form and failed a lot of tanks in the past when this method used to be more common.

if the air fill was dry, why / how would condensate form on the inside? I can see how condensation might take place on the outside if you did this when in a moist atmosphere, but not inside, and not underwater?

Andy

[Mark Chase]

Air fills are never that dry. If they were we wouldn’t be able to breathe them.

One turn open for me, just enough to equalise the set and just enough to allow a quick shut down. As for getting stuck in a hole and not being able the reach it.... That’s just not going to happen and if it did then shutting down probably wouldn’t help you.

Sudden balancing of tanks is not a good idea IMHO for all the reasons posted above, but if it makes you happy then why not? It’s definitely not a dangerous way to dive.

ATB

Mark Chase

[Digger]

Right then. A clear lead for my team. Thanks guys. Now we're starting to get into some of the reasons I should have come up with in my surface interval. I did mention the whole failing cylinders bit (Sabre setup tanks usually get binned by their second test because of the equalising) but no-one believed me.

18 to 5. I think we have a result.

[Diving Dude]

So all you guys and girls that voted to have the manifold either partly open or fully open what would you say to a new twinset diver who is maybe going to do thirty dives in six months
Either do about twenty dives in a puddle practising shutdowns and only then start proper diving in the sea or a couple in a puddle and then twenty eight in the salty stuff with the manifold shut, practising opening it.

After all the fun of diving is what you see not the mechanics of how you do it.