BridgeDiver29:
Hi all,
I am looking for experiences/recommendations/opinons on gas switching blocks.
My dive team recently made the move to full face masks to facilitate underwater communication and due to the regulations that we dive under, we must have access to an alternate, redundant gas supply. Obviously, we would like to be able to get to this without removing the ffm, and I am told that a switch block could be the way to do it.
Any information, especially personal experiance, would be appreciated.
Happy New Year!
A gas switching block is exactly what you're looking for. I am only aware of three that are widely available in the US:
KMDSI:
http://www.kmdsi.com/scuba.html
Sartek:
http://www.sarind.com/acatalog/rsv.html
Oxycheq:
http://www.mj-engineering.com/shop/
The Oxycheq block is actually manufactured by M&J Engineering and the link I listed is for their direct webpage. If you intended to use this block for multi-gas technical diving, the KMDSI block would be your best choice. It starts at $450, plus other odds and ends you'll need for hook-ups. However since you intend to use this simply to route a redundant air supply to your FFM and thereby avoid having to doff the mask in the event the emergency air becomes necessary, any of these blocks will suffice. The Sartek and Oxycheq valves each sell for $300-350, and between the two I'd recommend the Oxycheq because for the same price it is built like a tank.
However, there is another option that could save your team a bundle if you're willing to do a little extra footwork. I haven't seen it discussed here, but there is a dual tank valve from Ocean Reef (the Italian company that makes the Neptune FFM). Don't let that dissuade you-- I wouldn't recommend the Neptune, I use an AGA and so does my dive team-- but the reviews I've read of the gas block are all positive.
http://www.oceanreefgroup.com/dualtankvalve.html
Here's the catch, this item is not sold in the USA or Canada. I suspected it was a legal issue since it looks very much like the Sartek block. So I called up the Ocean Reef US sales rep and asked why it wasn't available since all of their other products were sold here-- she said it was a patent problem, and after more questioning admitted the dispute was with Sartek. So it is not available for direct sale in the US, but it is available if you do a little extra work. There are two reasons to do this, first because it has better connections than the Sartek block. The Sartek block comes with one Scubapro AIR-II type lp connection, whereas the Ocean Reef uses standard regulator inputs. As previously mentioned in this thread, it would be better to use commercial grade quick disconnects rather than BC-style lp connections. The Ocean Reef allows you to do this. But the main reason it's worth it to look into this option is simply the cost. I have yet to hear of a dive team where money is no object. The Ocean Reef valve lists for about $200-250, and may be had for less if you are patient. I just purchased one, new, from Ebay UK and had it shipped here for a grand total of $140. Scuba distributors in England/Europe may also be a good place to check if you're looking for a bulk purchase. Sea and Sea is a large UK scuba distributor that sells the dual tank valve for aproximately $225:
http://www.sea-sea.com/oceanreef/pricelist.php
Please note I do not know if they ship abroad-- send them an email and find out.
A couple other comments/tips regardless of which block you go with... First regarding quick disconnects: Hansen makes some of the best industrial high-flow connections, and are generally found on commercial diving QD whips. A good place to get these ready made is from Amron:
http://www.amronintl.com/
Look for their bail-out whips (part # BO-37B). I use this whip on both my primary 1st stage and redundant 1st stage, just for the ease of gear storage and transport. But I suggest at the very least that you get a QD for your redundant supply, so that in the event you need to pass off your pony bottle (say to an entangled diver) you can do so. (For this same reason your team should consider quick release pony mounts.) Also, you don't mention which FFMs your dive team uses, but if it's AGA masks here is another comment about QDs. One annoying thing about the AGA is that the 2nd stage reg connection is not the same as standard scuba regs. So you'll either have to use the specific lp AGA hose or make other arrangements if you want a QD on your mask. One common solution is to use the M&J swivel which has an AGA female and a standard scuba 9/16-18 male connection. That's what my dive team uses, enabling a connnection to QD whips. However, I have seen one of these swivels fail (please see my post on the ball swivel thread) and therefore I don't use one on my personal AGA. Instead I contacted the very nice folks at DECA diving who custom rigged a standard lp-to-AGA hose with a Hansen QD for me:
http://www.decadiving.com/
One last comment, I know this is long but I hope you find it helpful. Be sure to add an overpressurization relief valve ($15-20) to one of the lp ports on your primary 1st stage. In the event your primary reg fails (will your team be doing much ice diving?) and you have to switch the block over to your pony there will be no outlet for your primary and it will blow the lp hose if you do not have a relief valve. The octo or redundant 2nd stage will serve that purpose on your pony.
Good luck, feel free to contact me if you have questions.
