Decanting to a twinset

[Davey Willo]

Myself and a buddy are diving the Farnes off a harboat next weekend but the boat is staying out all day.. not a problem for us with twin 12's or even those diving singles as a spare cylinder is taken but my mate is running twin sevens on a BP/Harness etc and will definitely not get two dives out of them, so we intend to take a decanting whip and a charged 15ltr to hopefully recharge the sevens back up to a respectable pressure..

My question.... is there a routine for decanting to twins, I seem to remember reading somewhere that the best method is to isolate both cylinders, decant to them separately and then open the isolation valve again.... now did I really read this somewhere or did I just dream it??

thanx in advance
Dave

[Ali]

Hi Dave,
Yes that's the way to do it. Last year I charged my twin 10s this way from a 25L J cylinder and was abit disapointed as I only got an extra 60 Bar.
It will be interesting to know how you get on!

Ali  

[Andy Winterburn]

Dave

I sat down and worked out the 'sums' involved after Iwas a little disapointed in the amount of extra gas I gained after decanting. I think the difference was 10 bar in the manifold open to closed.
Your mate will struggle though, his twin 7's been 300 bar and the 15 been 232 as it will equalise to the 232. Dependant on how much is in the twins when he decants he might actualy loose gas

[Gavin Yates]

<font color='#000F22'>Dave,

He better be doing a short second dive ... I would estimate that you'll only be able to get about 120-140 bar in 'em.

I sometimes do top ups but it's usually to get a higher nitrox mix for second dives. I've found even topping them up mani closed does not boost a huge ammount.