Fill tank leaking air, help.

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Lobi

Lobi

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Feb 11, 2023
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Michigan
Didn't leak after first fill and charged my Shen Yang just fine. After getting tank filled second time (local dive shop) it now leaks air where the big threads go into the valve on the bulk air tank. Sorry for noob terms. Don't know what to call it. I'll include a picture showing where it seems to be leaking as I fill the gun. I did replace the o-ring inside this area with no change in it leaking.

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Replace that o-ring on the adapter. Run your little finger inside the tanks fitting (female) to see if there are any burrs in the metal. Emery cloth (fine) can smooth it out. Maybe try an o-ring with a SLIGHTLY thicker cross section. Try just flipping the o-ring over too (with some silicone grease, no petroleum based stuff)
 
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If it is leaking from where you show in the pic I think it has to be related to that oring and its seating surface - hard to tell from the pic and could be my imagination, but it kinda looks like the seat area could be a little buggered where maybe the handtight fitting was tightened too much and scored it. Gerry52’s suggestion of emory cloth should help correct that.

In addition to a little bigger cross section oring as Gerry52 suggests, you could also try the same size oring you are using now but in a durometer 90 instead of the usual 70 - it would reduce the chance of bottoming out.
 
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like others said, put a little silicone grease (NOT PETROLEUM BASED) on those orings. Little dab, thin coat. It doesn't take much. It will help the seals and give a little more life to those rings.
O-Rings and this PCP hobby go hand in hand. Get used to it. I keep a tackle box for just o rings. If I ever break down a part to replace a ring, I go ahead and replace all that associated with it while it's opened up. Good and cheap peace of mind.
 
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To me, that thread looks like a 1/4-14 NPT thread. When fully tightened do those two parts contact each other and capture the O ring so it’s out of sight ? If when tightened down, you can still see the O ring, it ain’t doin’ nuthin’.
If it’s an NPT thread like it appears you need 1 1/2 to 2 wraps of teflon tape on the male threads, then tighten, check for leaks. Do not allow tape to over hang end of male thread, it should be one thread back from the very starting groove of the thread. If teflon tape is overhanging it can end up going into your gun and foul things up.

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rcs9250 said:
To me, that thread looks like a 1/4-14 NPT thread. When fully tightened do those two parts contact each other and capture the O ring so it’s out of sight ? If when tightened down, you can still see the O ring, it ain’t doin’ nuthin’.
If it’s an NPT thread like it appears you need 1 1/2 to 2 wraps of teflon tape on the male threads, then tighten, check for leaks. Do not allow tape to over hang end of male thread, it should be one thread back from the very starting groove of the thread. If teflon tape is overhanging it can end up going into your gun and foul things up.

View attachment 332222
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Yes, that o-ring goes out of sight and the two parts lock up right and clean. Can't hardly tell it's two pieces. With the correct o-ring doing its job there, I don't think tape is needed.
Problem is, where to find the correct o-ring
 
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Lobi said:
Yes, that o-ring goes out of sight and the two parts lock up right and clean. Can't hardly tell it's two pieces. With the correct o-ring doing its job there, I don't think tape is needed.
Problem is, where to find the correct o-ring
Click to expand...
OK, if it locks up tight, that’s good. Correct, no tape is necessary.
 
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