J-Valve question

[james croft]

J-valves are still manufactured, being used by the military and often mandated by safety regulations in conditions where it is nearly impossible to read guages, etc. in commercial and PSD diving. I use them when vintage diving and they work as well as my K or more "modern' valves. Seems to me that the last time I checked a commercial diving catalog they were pretty expensive, selling for around $160.00 for one. Makes that 10.00 valve seem like a bargain. Recreational diver's badmouth the J-valve and tell you they will kill you, etc. but I have dove them over 35 yrs and had zero problems with them.

 

[Thalassamania]

Considering that most J valves don't just shut off at 300 or 500 or whatever psi but slowly restrict the air flow the Scuba Pro depth compensated reserve was more advertising hipe . At 100 feet ambient pressure is about 44 psi so if 300 psi is the start of the closing point it would be 256 psi above ambient at 100 feet. Not that significant a difference considering a 5000 psi SPG can easly be + or - 50 psi off with a 1% error which is considered normal in any gauge other than a high presision test gauge.

Caps got it right again.

 

[oly5050user]

If memory serves me:

1. You can change the spring in any of them.
2. 300 and 500 psi were standard.
3. The ScubaPro DCAR was a "Depth Compensated Automatic Reserve" which provided either 300 or 500 PSI (depending on the spring) over ambient.

DCAR "depth compensated ADJUSTABLE reserve" nothing automatic about it//no spring to change.top of valve has adjustment screw that when depressed and given 1/2 turn it created more tension on spring..yes it also compensated for depth to ambient pressure.

 

[Thalassamania]

DCAR "depth compensated ADJUSTABLE reserve" nothing automatic about it//no spring to change.top of valve has adjustment screw that when depressed and given 1/2 turn it created more tension on spring..yes it also compensated for depth to ambient pressure.

Thanks, memory is the first thing to go and I'll be damned if I can remember the second. Was the DCAR the valve that had the little "bar graph" pressure guage built into it?

 

[oly5050user]

yes.it had a small steel rod that went to an upright position when tank is fill and went lower as it emptieed.you cannot see it while in use-its behind your head but your buddy can..yes memory goes pretty bad after 50 as I too well know.

 

[Thalassamania]

yes.it had a small steel rod that went to an upright position when tank is fill and went lower as it emptieed.you cannot see it while in use-its behind your head but your buddy can..yes memory goes pretty bad after 50 as I too well know.

I thought so. That was a feature I liked. It saved the PIA of having to gauge the tank in the locker before you used it.

 

[Luis H]

The DCAR valves were great! I don't use them anymore, but I still have a couple of them.

You could take apart the reserve with a full tank as long as the valve was closed.

I used to temporarily trick them to hold about 50 to 100 PSI even if you open the valve and lower the reserve lever (basically replaced the stem with a dummy). This allowed my buddy and me to fly from Puerto Rico to the Virgin Islands without totally emptying our tanks. After we landed I would replace the proper parts and filled our tanks at any dive shop in the V.I. We didn’t need to waste time or money on a VIP. On the way back to PR it didn’t matter since I worked in a dive shop back then.

 

[anth]

The real question is...why would you want one?

I've used tanks with J-valves for benthic suction sampling, where a bare tank and valve without a first stage drives the suction sampler, an airlift of sorts. The J-valve keeps you from flooding the tank...

 

[captain]

Recreational diver's badmouth the J-valve and tell you they will kill you, etc. but I have dove them over 35 yrs and had zero problems with them.

I have 7 singles and 1 set of doubles and they all have J valves. There is no reason to not use them. If I am using an SPG I leave the lever down, if I am diving vintage I use the J reserve.

 

[GeorgeC]

One issue worth considering is the diver thinks the J-Valve is in the up (reserve) position when in actuality it is in the down (non-reserve) position. The valve or rod could have been inadvertently turned by snagging or just simply forgetting what is the correct position for reserve.

While underway the diver may not look at his SPG for whatever stupid reason thinking he has yet to feel the resistance of the low gas on the J-Valve. When the diver feels the resistance of the low air he goes to pull the J-Vave rod and realizes it is already in the non-reserve position. Panic sets in and who knows what is next.

Just a hypothetical…I realize it is a stretch for the diver not to look at his SPG until he is at 500 or so psi