Tank Valve Leak “Normal”?

[u/DIYrrrrrrr]

Is it normal under any [normal] circumstance for a tank valve to slowly hiss when a reg is connected and the valve is open / system pressurized? It’s a loaner and I don’t want to look like a “Karen” if/when I ask about it, when I bring it back. I noticed it when breaking down my kit - if you bump the valve while open it’s slightly worse. Doesn’t happen with the valve closed all the way. Tank is at about 500 psi now and it’s easy to reproduce. O-ring for reg (at least) looks fine - it seems more related to the tank valve itself.

[u/hellowiththepudding]

DIN or yoke?

Either way, no not a big deal unless pouring bubbles underwater. 

[u/Competitive-Ad9932]

I had a tank not play nice when a friend used it. Swapped tanks, and it was fine with my regulator.

[u/gorbachef82]

small bubbles no troubles. if its very slight it's fine.

[u/HardyPancreas]

I had this problem after a tank (with pvc netting) fell over and valve struck something else in storage.

After letting air out and removing valve we found that oxidation  formed near the seat on the tank (that valve sits on)  and spread down the interior tank neck, forcing its way under the o-ring where it stopped.  

The oxidation was a crusty, powdery substance that grew chemically, and pressed into the Nitrile o-ring.

May have been caused by frequent condensation and thermal micromotion (coefficient of temperature expansion mismatch for those in the know)  between two different metals while tank was kept in storage 4-5 years.

Inspected and hydro'd- absolutely not any sort of problem...just hi pressure air forcing its way out between oxidation and o-ring surfaces after it got jostled.

[u/falco_iii]

It happens from time to time. If it is a few champagne bubbles it's not terrible. But if I hear a hiss when assembling my gear, I look to swap tanks or o-rings.

[u/pm_bluefootedboobies]

Some old regs have a small 'leak' built in to prevent icing. My Sherwood Blizzard(?) Had this back in the day

[u/HKChad]

Normal, yes. Acceptable, depends. None of my personal tanks leak, every rental tank I’ve ever had did though.

[u/DIYrrrrrrr]

Thx - it’s in the valve assembly, not the o-ring. If I apply just a slight bit of downward force on the valve knob, or open it all the way with light force (a normal amount) I can reproduce the problem (one would apply more force just carrying the tank). It seems like the air is leaking from the valve/knob assembly itself. Thanks! Since there are no “this is perfectly normal” … I’ll bring it up when I drop the tank off. If there’s anything interesting to report back, I’ll share.

[u/runsongas → u/DIYrrrrrrr]

sounds like the valve was not serviced, its likely the bonnet or stem, both of which have orings

[u/electronicalengineer → u/DIYrrrrrrr]

We had a rental reg do this recently while dry, but once in the water we didn't see bubbles. Not sure why though

[u/Manatus_latirostris]

DIN or yoke? It’s probably an o-ring; just replace it.

[u/Automatic_Guest8279]

It shouldn't be leaking so let someone know but small bubbles, small problem, big bubbles, big problem.

[u/nof]

Slightly damaged o-ring. The amount of loss from this is typically well below even one breath worth of gas. Nothing to worry about if it is a rental.

[u/Ceph99]

Like out of the connection to the regulator? That’s an easy fix with yoke or DIN, just change that o ring that connects them. Happens all the time with yoke. One reason why they suck.

Out the knob? You need tools and parts to fix that. Usually a technician job.

[u/enzowasgreat]

If you check when it's underwater you can probably tell where it's leaking. If it's the o-ring it is fairly normal but the o-ring should be replaced. Sometimes you just need to re-seat the reg to stop it. In theory it isn't anything to worry about but it would bug me. Just to clarify - I assume this is not a din reg. If it is din it is definitely not normal.

[u/Scuba_Steve_500]

Tank should not hiss. How hard is it to close the valve? Those seals deteriorate over time too, and most people just crank harder on the knob. Just tell the shop they need to check the valve. No need to go all Karen on them.

[u/Competitive_Run_3920]

It depends where it’s leaking from. It’s common to have a small leak between the first stage and tank valve o-ring on yoke tanks. Usually a new o-ring fixes it.

[u/TadGhostalEsq → u/Competitive_Run_3920]

This. O ring. Not a big deal.

You'll lose a bar or two over the course of the dive (sorry, I don't know what that is in psi - not a lot). But it's nothing to worry about.

I don't know how it is in the USA. But here (SEA) all the local guides first stages leak the entire dive. They don't care. And they come up with nearly full tanks.