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Old 5th March 2008, 01:31   #1
bobby
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Very Very Slow Leak

I have a very slow leak on my left CL. It passes positive and negative tests with no issue. If I leave the unit sit for an hour on a negative test the lung will expand. I can hear a small tick every 2 or 3 seconds but can't find the leak. It seems to be right by the "T" but I can't tell if it is the lung or the "T". I have pulled all the O-rings and have no issues there. My next step is to fill with HE unless someone else knows a trick to finding it that I don't.

I have taken the unit on dives and had a buddy look for the leak and could not find a single bubble as well as no water of any consequence in the lung. I would like to find the source though before it becomes a bigger issue on a longer dive.

Bobby
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Old 5th March 2008, 01:55   #2
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Re: Very Very Slow Leak

I am not sure I am being helpful, but when I am looking for REAL SMALL leaks, I mix up some dish washing soap and water and spray where I think a leak is and look for bubble development. You can see super small leaks this way. Have never tried this on a rebreather though. YMMV
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Old 5th March 2008, 02:27   #3
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Re: Very Very Slow Leak

Check the DSV to make sure that there isn't a slow leak somewhere in there. I know the DSV on my O2ptima would let a very small amount of air in from the ambient air on + and - checks which caused the mushroom valves to tick. Wasn't an issue, but an annoyance. When I switched to the Golem BOV it went away.

I took me a while to pinpoint where the ticking was coming from as sound travels and bounces in the loop.

Just a thought...

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Old 5th March 2008, 02:48   #4
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Re: Very Very Slow Leak

Spray it down with the soapy water while you put positive pressure on the loop via exhaling into the DSV. The OPRV will allow the excess escape pressure to escape, but it will keep the loop at maximum pressure. You should get some bubbles if there is a leak somewhere other than the OPRV.

To check for a small negative leak, put paper towels inside the CLs, the hoses, etc. Put a vacuum on the leak by inhaling on the DSV, and then shut the DSV. Submerge it in a tank or pool for a while, then pull it out and check where the paper towels are wet. It will put you in the general area of the leak for further inspection.

I've found a pin hole in a loop hose that was not noticeable during a visual inspection. They sometimes develop where the hose attaches to the plastic T-pieces or threaded collars due to stress placed there when the unit is sitting with the looped draped down in front and not up in the mouth.

Just some ideas.
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Old 5th March 2008, 07:27   #5
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Re: Very Very Slow Leak

Richie's advice is spot on, ticking is generally the sound of gas being sucked in through the dsv, the reason you 'hear' it up at the T-piece is that the sound travels within the exhale hose like an amplifier.

A quick strip of your DSV, a wash of all parts in warm soapy water to remove the grease followed by new greasing with silicone grease and a rebuild should solve this for you.

Your instructor will have shown you how to do this on your course, it is a common problem with the Meg and other rebreathers using DSVs of a similar design.

Cheers,

Dave Cooper.

 
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Old 5th March 2008, 08:25   #6
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Re: Very Very Slow Leak

you might also want to look at this thread

http://www.rebreatherworld.com/showthread.php?t=9923

of a leak I had from the t-piece. mine was there from new and was a small manufacturing flaw, easily resolved with bit of sand paper once I knew it was there.

Stephen
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Old 5th March 2008, 19:03   #7
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Re: Very Very Slow Leak

Thanks everyone for all of the good suggestions on where to look. I will strip it down tonight and see if I can find it. I just readjusted my hoses going into my T's a while back so this may have started the problem. I have not let the unit sit over night with negative pressure on it for a few dives so I may have had the problem for a while and not realized it.

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Old 8th March 2008, 04:54   #8
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Re: Very Very Slow Leak

My apologies for not posting the results. I had to go out of town on business and did not get to the unit until this evening. The leak was a from the exhale inlet tube. I had adjusted the hose on the tube for better hose routing. I may have actually had the leak all along and not noticed it. The reason for the leak was a groove left on the "T" from lathe manufacturing. I found the leak by a negative test with the "T's" swapped on my counter lungs. That told me that is was in the loop and not the counter lungs. I took the short route since I had adjusted the exhale lung recently. I pulled it apart and inspected the "T" closely. I found a tail groove from machining and turned it out to a smooth finish. After running a negative test for over an hour I had no more leaks.

In reality the leak was so small I don't believe it would have allowed water in with some pressure in the lungs. It is nice to have found the source though. Again thanks to everyone for giving idea's for where to look.

Bobby
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Old 8th March 2008, 07:16   #9
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Re: Very Very Slow Leak

Yea I have one of those at the moment in the Right hand lung.

Mine is a pin hole leak in the back of the lung, god know how it got there but I don't .

Took me forever to find it and would be impossible to get to to glue up as its about half way down the lung.

I gave in and have a new lung on its way over.

Cheers
Chriso
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Old 8th March 2008, 12:28   #10
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Re: Very Very Slow Leak

Quote: (Originally Posted by Chris) View Original Post
Yea I have one of those at the moment in the Right hand lung.

Mine is a pin hole leak in the back of the lung, god know how it got there but I don't .

Took me forever to find it and would be impossible to get to to glue up as its about half way down the lung.

I gave in and have a new lung on its way over.

Cheers
Chriso
A drop of Aquaseal on the outside should fix it just fine.
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