Why no regulator shutoff?

[windapp]

My dive buddy and I were talking, and we have a question. Why is there no shutoff on the second stage regulator? I would think that it would be very useful if your regulator started freeflowing at 100 feet right at the end of your dive. You could just shut it off, and switch to your octo, and finish the dive with a normal accent. Anybody know why we don't do this?

 

[matt_w]

My dive buddy and I were talking, and we have a question. Why is there no shutoff on the second stage regulator? I would think that it would be very useful if your regulator started freeflowing at 100 feet right at the end of your dive. You could just shut it off, and switch to your octo, and finish the dive with a normal accent. Anybody know why we don't do this?

I think many people will believe this creates more problems then it solves. In 99% of recreational dive scenarios, you can make a safe normal ascent with a free flowing second stage. If you can't you can always share air with your buddy. If you have no buddy you have either a redundant air supply and/or the ability to cut of the free flowing second stage.

If you are concerned about it, you could dive an h-valve on a ingle tank with independent regulators. You will want to have regular practice shutting down valves though.

 

[tbone1004]

extra things to go wrong in normal diving. it's rare that a second stage will truly freeflow uncontrollably. There are shutoffs made though
Regulator Shut Off Adapter, Piranha Dive Manufacturing

$20. Useful on things like stage and deco bottles which are more apt to second stage problems. I do know some buddies that have taken to using quick disconnects on the second stages though so if one goes bad they can just swap it underwater. First breath is a little wet, but oh well

 

[adelman]

One reason for an apparently 2nd stage free-flow *could* be an actual 1st stage free-flow. Depending on the design, the 2nd stage may be designed to respond to the over pressurization of its supply by releasing that pressure as a free-flow. If you were to shut off or disconnect such a 2nd stage, you'd just move the free-flow to the alternate second stage. If there wasn't an alternate, you'd probably violently burst a hose.

In any system where you have a 1st stage with no 2nd stage (or a 2nd stage not designed to release the pressure), you should have an over-pressurization valve in place at the 1st stage. So now you've added a shutoff or disconnect, and an over-pressurization valve, ... two more potential failure points.

 

[Dan W UTD]

I think many people will believe this creates more problems then it solves. In 99% of recreational dive scenarios, you can make a safe normal ascent with a free flowing second stage. If you can't you can always share air with your buddy. If you have no buddy you have either a redundant air supply and/or the ability to cut of the free flowing second stage.

If you are concerned about it, you could dive an h-valve on a ingle tank with independent regulators. You will want to have regular practice shutting down valves though.

Agreed. Also, at 100ft and deeper you start to need more gas to cover rock bottom gas planning than a single tank can supply. Doubles start to make more sense in this range. For instance, at 100ft on an aluminium 80, you'll need about 1500psi to get two divers safely back to the surface. With a set of DIR doubles you are able to shut off either post or isolate one tank in the event of a failure and make a safe ascent. Practice to build muscle memory is key with whatever rig you dive.

 

[fjpatrum]

Because if it can be turned off, it will be. And I guarantee it will be turned off at the wrong time. Freeflows really aren't that big of an issue to deal with. They're noisy and make visibility a pain but more often than not (from my limited experience) they can be stopped relatively easily.

 

[Bedros A]

I would just like to add that in Worst case scenarios you can actually breathe during the free flow (I think as taught during OW class)...that might come in handy during catastrophic failures...

BA

 

[*dave*]

This is the only reason needed to make this a bad idea:

One reason for an apparently 2nd stage free-flow *could* be an actual 1st stage free-flow. Depending on the design, the 2nd stage may be designed to respond to the over pressurization of its supply by releasing that pressure as a free-flow. If you were to shut off or disconnect such a 2nd stage, you'd just move the free-flow to the alternate second stage. If there wasn't an alternate, you'd probably violently burst a hose.

In any system where you have a 1st stage with no 2nd stage (or a 2nd stage not designed to release the pressure), you should have an over-pressurization valve in place at the 1st stage. So now you've added a shutoff or disconnect, and an over-pressurization valve, ... two more potential failure points.

I've seen lots of free flows, but they were all due to a first stage freeze.

Gas temperatures can reach -50f as they expand in the first stage. If the ambient temperature is not sufficient to keep the first stage from icing, the piston can freeze and there will be no reduction of pressure going to the second stage. Whichever second stage is tuned the lightest will freeflow. Usually, this will be your primary.

Free flows are a huge issue in terms of gas loss. I've seen 1000psi/min loss rate from a diaphragm regulator on an Al80, so whatever your response is, it needs to be rapid. For me, that would mean shutting down the gas supply and sharing with my buddy till the reg thawed out.

 

[cloudflint]

I have a regulator shut-off in the form of my tank valve, if I get a freeflow i just turn the valve and problem solved

 

[Tortuga68]

...and you breathe from what then?