Twin sets vs H or Y valves

keylimepie · December 8th, 2005, 12:08 PM

OK, first question - hope it's not too stupid!

Just wondered what the advantages are of a manifolded twin set over a single cylinder with an h or y valve. My undertsanding is that with an h or y valve you can close down one side if you get a freeflow, for example. In principle, this sounds like the same option you get with the twin set - but with the proviso that you have a separate tank on each side/first stage). Is it that you run the risk of losing all of or a lot of the gas in what might be your only cylinder, whereas with the twins you (probably) have more gas and can quickly save the gas in one cylinder by closing the isolation valve? (Not sure if I have answered that myself

). And, when DIR divers dive on one cylinder do they use an h or y valve setup?

Cheers

Dave

*Clare Gledhill* · December 8th, 2005, 01:06 PM

Quote: (Originally Posted by keylimepie)

Is it that you run the risk of losing all of or a lot of the gas in what might be your only cylinder, whereas with the twins you (probably) have more gas and can quickly save the gas in one cylinder by closing the isolation valve?

Quote:

(Not sure if I have answered that myself

).

I think you did

***EBT*** · December 8th, 2005, 02:04 PM

An H/Y valve is still vulnerable to a tank neck O ring failure. Thats what the isolator is for on an isolation manifold.

*JohnKendall* · December 8th, 2005, 02:07 PM

One other thing to consider is how easy it is to shut down. A single cylinder valve is further back from you than a twinset, and with 2 regs on a y-valve you may have issues geting to the valves to shut them down.

My advice would be to go for a small twinset rather than a single with H or Y valve.

J

Rob Dobson · December 8th, 2005, 02:30 PM

And don't forget you have a nice distribution of weight with twins and can potentially carry more back gas (for your team as well as yourself).

keylimepie · December 8th, 2005, 08:32 PM

Thanks for the replies folks, although I'm now worried I'm beginning to think like a DIR diver and I've only been registered for 2 days

The words BORG and assimilation spring to mind

or perhaps I shouldn't post after watching Star Trek :D

Chrisch · December 14th, 2005, 12:06 PM

Quote: (Originally Posted by JohnKendall)

One other thing to consider is how easy it is to shut down. A single cylinder valve is further back from you than a twinset, and with 2 regs on a y-valve you may have issues geting to the valves to shut them down.

My advice would be to go for a small twinset rather than a single with H or Y valve.

J

That depends on the valve. Some of them are very wide and give a similar knob position to a manifold. (Ooh er..) Personally I find it as easy if not easier to shutdown with a regular H valve as with twins. Just make sure the (single) tank is high enough.

That said the small twinset is a "nicer" option if you can afford it!!

Chris

rhinopias · December 14th, 2005, 12:19 PM

I go for both. I have a twinset that is pretty standard and a very stripped down single tank set-up for shore dive pootles and stuff like that.

I am not sure that the H-valve is worth the hassle if you are doing "simple" dives and I don't think the H-valve is a good compromise if the accepted wisdom for the dive says that you "need" a twin set.

mstroeck · December 14th, 2005, 12:38 PM

Quote: (Originally Posted by Chrisch)

That depends on the valve.

Exactly. It's not much of a problem with one of these, for example:

(Available here: http://www.beaversports.co.uk/catalo...der_valves.htm)

**jb2cool** · December 14th, 2005, 03:18 PM

for ultra-redundancy you could have a twinset with H/Y valves on each cylinder. Then you can have 4 first stages in your setup

.

Might be a bit overkill though.

:D

:p

December 8th, 2005, 12:08 PM	#1 (permalink)
keylimepie(Offline) New Member Join Date: Dec 2005 Location: Sunderland Posts: 123	Twin sets vs H or Y valves OK, first question - hope it's not too stupid! Just wondered what the advantages are of a manifolded twin set over a single cylinder with an h or y valve. My undertsanding is that with an h or y valve you can close down one side if you get a freeflow, for example. In principle, this sounds like the same option you get with the twin set - but with the proviso that you have a separate tank on each side/first stage). Is it that you run the risk of losing all of or a lot of the gas in what might be your only cylinder, whereas with the twins you (probably) have more gas and can quickly save the gas in one cylinder by closing the isolation valve? (Not sure if I have answered that myself ). And, when DIR divers dive on one cylinder do they use an h or y valve setup? Cheers Dave

December 8th, 2005, 01:06 PM	#2 (permalink)
Clare Gledhill(Offline) GUE Instructor Site Admin Pacman Champion! Join Date: Nov 2005 Location: UK Posts: 1,540	Quote: (Originally Posted by keylimepie) Is it that you run the risk of losing all of or a lot of the gas in what might be your only cylinder, whereas with the twins you (probably) have more gas and can quickly save the gas in one cylinder by closing the isolation valve? Quote: (Not sure if I have answered that myself ). I think you did __________________ Clare . "Keep away from people who try to belittle your ambitions....Small people always do that, but the really great make you feel that you too can become great." Interested in DIR dive training? Always happy to chat/answer questions so get in touch via PM or visit www.dirdiver.co.uk

December 8th, 2005, 08:32 PM	#6 (permalink)
keylimepie(Offline) New Member Join Date: Dec 2005 Location: Sunderland Posts: 123	Thanks Thanks for the replies folks, although I'm now worried I'm beginning to think like a DIR diver and I've only been registered for 2 days The words BORG and assimilation spring to mind or perhaps I shouldn't post after watching Star Trek :D

December 14th, 2005, 12:38 PM	#9 (permalink)
mstroeck(Offline) New Member Join Date: Nov 2005 Location: Vienna, Austria Posts: 156	Quote: (Originally Posted by Chrisch) That depends on the valve. Exactly. It's not much of a problem with one of these, for example: (Available here: http://www.beaversports.co.uk/catalo...der_valves.htm) Last edited by mstroeck; December 14th, 2005 at 12:44 PM.

December 14th, 2005, 03:18 PM	#10 (permalink)
jb2cool(Offline) Padawan learner Join Date: Nov 2005 Location: Bracknell, Berkshire Posts: 796	for ultra-redundancy you could have a twinset with H/Y valves on each cylinder. Then you can have 4 first stages in your setup . Might be a bit overkill though. :D :p __________________ http://jb2cool.bulldoghome.com

December 8th, 2005, 02:04 PM	#3 (permalink)
*EBT*(Offline) Just another crouton... Join Date: Nov 2005 Location: Brighton Posts: 413	An H/Y valve is still vulnerable to a tank neck O ring failure. Thats what the isolator is for on an isolation manifold.

December 8th, 2005, 02:07 PM	#4 (permalink)
JohnKendall(Offline) GUE Instructor/DIRX Moderator Join Date: Nov 2005 Location: Cambridge, UK Posts: 1,097	One other thing to consider is how easy it is to shut down. A single cylinder valve is further back from you than a twinset, and with 2 regs on a y-valve you may have issues geting to the valves to shut them down. My advice would be to go for a small twinset rather than a single with H or Y valve. J

December 8th, 2005, 02:30 PM	#5 (permalink)
Rob Dobson (Online) Chillin' with the ninjas Join Date: Nov 2005 Location: Oxford Posts: 535	And don't forget you have a nice distribution of weight with twins and can potentially carry more back gas (for your team as well as yourself).

December 14th, 2005, 12:06 PM	#7 (permalink)
Chrisch(Offline) Hogarthian Heretic Join Date: Dec 2005 Location: Brighton Posts: 104	Quote: (Originally Posted by JohnKendall) One other thing to consider is how easy it is to shut down. A single cylinder valve is further back from you than a twinset, and with 2 regs on a y-valve you may have issues geting to the valves to shut them down. My advice would be to go for a small twinset rather than a single with H or Y valve. J That depends on the valve. Some of them are very wide and give a similar knob position to a manifold. (Ooh er..) Personally I find it as easy if not easier to shutdown with a regular H valve as with twins. Just make sure the (single) tank is high enough. That said the small twinset is a "nicer" option if you can afford it!! Chris

December 14th, 2005, 12:19 PM	#8 (permalink)
rhinopias(Offline) New Member Join Date: Nov 2005 Location: London Posts: 2	I go for both. I have a twinset that is pretty standard and a very stripped down single tank set-up for shore dive pootles and stuff like that. I am not sure that the H-valve is worth the hassle if you are doing "simple" dives and I don't think the H-valve is a good compromise if the accepted wisdom for the dive says that you "need" a twin set.