Can’t stop MFL leak

[BryanEBIAB]

I’m expanding my system to accommodate a second keg to force carb while in storage. I picked up some QDs from Amazon and can’t stop them from leaking at the MFL connection. I have tried every combination of the following:
A) cranked down like hell on it—I think I may have even busted one as the metal now spins a bit in the plastic housing. *shrug*
B) added one of those little nylon washers, even though these have “built-in” washers and shouldn’t need it since it’s metal/plastic.
C) smeared a little keg lube on it. Helped a little but not enough.

So…
1. I read you’re not supposed to use Teflon tape with MFL but should I?
2. Is this just a manufacturer’s defect (shame on me for buying from Amazon)?
3. Am I dumb and don’t know about X?

 

[wdavis2003]

I've used these before with no problems. Have you checked the keg side to make sure all O-rings are on the posts and the posts screwed tightly? The little pop its and springs are correctly in place? You may have a damaged o-ring.

Edit: You may also have the spring upside down

 

[ITV]

Does your other liquid ball lock leak as well?

I stick with CMBecker ball lock disconnects since I have had good luck with them.

 

[day_trippr]

1. I read you’re not supposed to use Teflon tape with MFL but should I?
2. Is this just a manufacturer’s defect (shame on me for buying from Amazon)?
3. Am I dumb and don’t know about X?

1. There is no point in using tape or goop on MFL threads as there is a big hole in the middle of the swivel nut that is not ever sealed.
2. I'm thinking something is defective here, don't know what.
3. I don't think this is user error.

I also use only CM Becker QDs with flare stems. I have somewhere around 36 of their QDs in service between a keezer and three fridges and none of them have issues...

Cheers!

 

[BryanEBIAB]

It’s leaking from the flare fitting, not the post. It leaks when it’s not even on the post. Honestly, haven’t even tried yet.

 

[ITV]

It could be a hairline crack in your QD.

 

[BryanEBIAB]

I tried a “known good” QD and it still leaks. The common factor here is the barb/female side of the connection. Visually looks fine—smooth and polished where it interfaces the washer—but I guess not good enough. I’ll scrounge up another one and see what happens. This set came with two and they both leak in pretty much the exact same way so maybe a bad batch? Nothing significant in the Amazon reviews. Buyer beware.

 

[sibelman]

So if the leak is definitely at the barb/female side, what about how you've fastened your tubing to the barb? Overtightened hose clamps can leak. Oetikers have been completely reliable for me. I know this is a long shot, but something ain't right. Pictures?

 

[BryanEBIAB]

It’s the flare-end of the barb/flare piece. The barb side is okay…wish it were a little more “oversized” but it’s at least not presently leaking. I’ve tried 3 different QDs including an older one that I know at least doesn’t leak. Pictured below is where the bubbles are coming from (the bubbles themselves were hard to snap a photo of).

 

[day_trippr]

Uncanny. And you say those QDs have captive gaskets at the tips of their male flare threading?
Weird...almost seems improbable...

Cheers!

 

[Bobby_M]

how about a picture of the MFL tip and the inverse cone on the barb?

 

[BryanEBIAB]

Ugh, so after screwing around dismantling a reassembling, it seems like perhaps I got something to seat better and I’m not getting any leaks. Maybe all the cursing helped. I’ll leave it with some pressure in the line overnight and see if it holds.

Uncanny. And you say those QDs have captive gaskets at the tips of their male flare threading?

Nah, much less sophisticated. The end of the fitting is just tipped with plastic. Not “supposed” to need a washer but I feel like this might be the issue. It seems like a difficult surface to make a good seal against. Getting a little angry at it maybe dislodged some imperfection or maybe I just got lucky on the 10th time I tried seating it.

 

[sibelman]

This is quite a strange event. It seems that the geometry of one (both?) components is off somehow. The fact that the connection (usually) fails with different QDs points to the flare-swivel. Or what's behind door #3...

Clearly, some components need to be replaced.

I've never experienced a leak between a QD (all CMB in my case) and a flare-swivel. As long as it's not cross-threaded it should seal with a modest amount of torque and no tape, goop, or gasket/washer.

I feel for you, @BryanEBIAB . These kind of frustrations can drive me wild.

 

[BryanEBIAB]

Pressure is still holding in the lines at 20 PSI after about 12+ hours. In conclusion, I bought cheap on Amazon and something between the flare swivel and the QD is finicky. I suspect the flare swivel is deformed and needs to find the "sweet spot" against the QD's plastic surface.

For those who find this thread in the future, the lesson I learned today is "don't buy cheap". No branding on these QDs at all. Makes me miss my LHBS who I could trust would carry quality stuff. If anyone in Suffolk County, NY is thinking about opening one, I'll be a regular!

 

[camonick]

For those who find this thread in the future, the lesson I learned today is "don't buy cheap". No branding on these QDs at all.

I just purchased some pinlock QDs on Amazon and while the discount versions were tempting at half the price or less, I’m glad I paid extra for the CMB brand. I already have quite a few in service and have never had any troubles with them.

 

[mac_1103]

I bought these on Amazon. Do they qualify as cheap? They don't leak. So far anyway.

 

[BryanEBIAB]

I bought these on Amazon. Do they qualify as cheap? They don't leak. So far anyway.

Those are exactly the ones I’m dealing with.

 

[mac_1103]

Interesting...

 

[day_trippr]

Probably a manufacturing process variable with attendant defect rate and that wasn't addressed by Quality Control before crap got out the door...

 

[mac_1103]

Probably a manufacturing process variable with attendant defect rate and that wasn't addressed by Quality Control before crap got out the door...

There is (at least) one review on Amazon that seems to indicate (at least) one bad batch. Sounds like it was a different defect, but the seller replaced the bad ones and the customer was satisfied with the replacements. OP should drop them a line.

 

[IslandLizard]

Anyone having trouble with these "cheap" Amazon ones, have you tried a (plastic) flare washer (aka fish-eye washer) between the tippy of the QD and the swivel flare. Although a flare washer is not necessary in that place (the tippy on the QD acts as one), the added flare washer may help making a positive seal, or iron out any surface mating issues.

Also check for any (leftover) casting seams on the tippy of the QD. They can be sanded off such as with fine grit (dry/wet) sandpaper or fine emery board.

 

[BryanEBIAB]

Anyone having trouble with these "cheap" Amazon ones, have you tried a (plastic) flare washer (aka fish-eye washer) between the tippy of the QD and the swivel flare. Although a flare washer is not necessary in that place (the tippy on the QD acts as one), the added flare washer may help making a positive seal, or iron out any surface mating issues.

Also check for any (leftover) casting seams on the tippy of the QD. They can be sanded off such as with fine grit (dry/wet) sandpaper or fine emery board.

I did have a couple of those washers on hand and they improved the situation but it still leaked. Ultimately the no-leak situation I have now is with no washer. *shrug*

 

[Brewdog80]

I would purchase a bottle of plumbers sealant. It is a non hardening sealant that is safe for drinking water. Put a dab around the male threads and it should eliminate the leaks. Should.....

 

[IslandLizard]

I would purchase a bottle of plumbers sealant. It is a non hardening sealant that is safe for drinking water. Put a dab around the male threads and it should eliminate the leaks. Should.....

Sorry, that won't help. The threads don't make the seal, the 2 flare surfaces do. The threads only keep them tightly together.

 

[day_trippr]

How do people keep ignoring that hole in the middle of the swivel nut that is NEVER SEALED??

Cheers!

 

[IslandLizard]

How do people keep ignoring that hole in the middle of the swivel nut that is NEVER SEALED??

Cheers!

The swivel nut is clamped tightly against the barb's flange that fills the hole... /s

 

[day_trippr]

Riiiiight

 

[BryanEBIAB]

The seller reached out and wants to replace them. I’ve used these guys plenty and they’re not trying to cheat anyone, I think they maybe the consistency isn’t great. You get what you pay for.

 

[DuncB]

I've not had problems with the Kegland MFL push fit tube to screw onto the ball lock.

But I do use EVA barrier tube rather than that large diameter tubing which looks as if you could push it over the MFL and put the jubilee / worm clamp on directly.