Tank o-ring burst, turn off tank or not?

A month or two ago, I was assisting with an AOW class, where the o-rings on one of the student's yoke tanks burst underwater. I signaled the instructor that there was a problem with one of the students, who immediately got me to air share with her while he turned off her tank. I then ascended with her and escorted her back to the boat to get a fresh tank.

However, I now have some questions about turning off the tank. Would turning off the tank valve result in water ingress into the first stage, after the air in the first stage has escaped, due to the seal now being broken? I'm thinking that keeping the tank turned on and the regulator remaining pressurized would prevent the water from getting in at the cost of more air escaping from the tank during the ascent. If the regulator in question belonged to me I might have opted for keeping the tank on so that salt water doesn't get in, assuming my understanding of what will happen if the tank is turned off is correct.

FYI, this happened at the start of the dive, only about few mins in and we were relatively shallow, about 10m, so we had plenty of air to get back to the surface and to the boat.

Another thinking diver! Good question.

Some trade-offs:
- That huge rush of bubbles is annoying.
- As you ascend, expanding air in the first stage would minimize water incursion.
- Salt water inside a regulator should be attended to in a timely manner, but it won’t be instant damage. How readily available is a tech?

Perhaps a compromise? Turn the valve mostly, but not all the way off.

We generally do weekend trips, so a tech would be max 2 days away. Just thinking about what the best course of action would be if/when this happens to me, especially on a longer personal trip where I might not have spares on hand or access to a tech. Good point on the expanding air, didn't take that into consideration.

This happened to one of my divers once. The freeflowing gas still provided enough air into the reg that he could breathe normally and we made a safe, although bubbly, ascent without touching his gear.
I'd recommend keeping the air on unless the bubbles are an issue. We service tanks and regs all the time that have water introduced to them and while it is still an issue that needs to be dealt with, I'm not a big fan of isolating an air source underwater.
Keep the air on until at the surface, breathing is what is most important, take care of the gear after the people.

darrenlowjq:

...especially on a longer personal trip where I might not have spares on hand or access to a tech.

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flaw in the plan....

I like scuberd's answer better than mine.

darrenlowjq:

We generally do weekend trips, so a tech would be max 2 days away. Just thinking about what the best course of action would be if/when this happens to me, especially on a longer personal trip where I might not have spares on hand or access to a tech. Good point on the expanding air, didn't take that into consideration.

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My 2 cents from a recreational perspective: If I had a little salt water incursion into the first stage after the scenario described, and I had a couple dives left to do on a weekend trip.... I'd probably shrug and just do the dives, and then service the regulator immediately after the trip; that is if I was certain that salt water had even entered the first stage. There is a pretty good chance in the scenario described in this thread that no water would enter the 1st stage.

Salt water is certainly not "wonderful" for the internals of your 1st stage, but will not instantly destroy it or render it unsafe. I'd just test it carefully after the dive, and then before each subsequent dive. It should be fine.

Note: Valve o-rings can fail, but usually fail when the valve is first opened. If they fail underwater, the best course is to immediately begin ascending (at a safe rate), hopefully with your buddy ready to share air with you if needed. Hopefully your buddy is attentive and nearby... I would not waste any time before beginning my ascent. If I had allowed my buddy to wander off, I'd simply ascend solo.

Remember, there is unlimited air at the surface, but only a limited amount in your tank. Don't muck around at depth if you develop a significant "leak". Start moving towards the surface (hopefully with your buddy!) immediately so that a controlled ascent does not need to turn into a CESA.

Best wishes.

Water incursion into the reg set would not be a problem for me. After the days diving I'd simply disassemble, clean, and reassemble. I also carry a full service kit for my 1st & 2nd stages on anything more than a day trip. Dive time to me is way too precious to give up because equipment needs servicing. That said - I guess no one took a look at the tank ring before attaching the reg????? Not good form.

Do not turn the tank off, continue to breath normally and execute a normal rate ascent. Assuming you have a buddy, he/she should be alerted to the situation by the cloud of bubbles emanating from your rig and he/she should accompany you on your ascent.

The equipment is quite rugged, if you are away on a trip and no service is possible, the regulator should continue to function normally even if it did get little saltwater in it. When you get home have it serviced.

N

leave the valve on. though it may look bad, your student could have easily made it back to the surface w/o buddy breathing. it takes a loooooong time to dump a whole tank with a leaking o-ring.

a great experience for him. classroom learning is one thing, working thru the actual problem, priceless.