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DUOTIGHT LEAKS......

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h22lude

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Thread tape isn't meant to stop leaks. It is meant to help straight threads tighten enough so they don't leak. More of a lubricant

As @day_trippr mentioned, no washer is needed. Hand tighten then give them a slow turn with pliers. If you do it to fast or hard, you can ruin the plastic threads so go slow and turn just enough until you get more resistance. Shouldn't leak at all.
 

jddevinn

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I put these in when I first assembled the CO2 side with the duotight. They make it VERY easy (for me) to over tighten the fitting.
 

Deadalus

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8 mm=0.315 in. The fitting size listed in inches is 5/16"=0.3125". If the OD of the tubing is actually 8mm, the tubing would be 0.0025" larger than a 5/16" ID female fitting. I mention this without knowing for sure what the actual/exact ID and OD measurements are on the parts.
 

IslandLizard

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I put these in when I first assembled the CO2 side with the duotight. They make it VERY easy (for me) to over tighten the fitting.
I wonder if dropping in a (small) properly sized o-ring, instead of the fish eye washer, would create a better positive seal, while preventing the risk of over-tightening?
When sealing (semi-)hard surfaces against each other, with nothing to compress, there's not much to give. 1/16-1/8 of a turn could start stripping the threads, or put more stress on them than they are designed for.
 

jddevinn

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The tubing and the fittings being discussed come from the same manufacture and are intended to use together.
 

jddevinn

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I wonder if dropping in a (small) properly sized o-ring, instead of the fish eye washer, would create a better positive seal, while preventing the risk of over-tightening?
When sealing (semi-)hard surfaces against each other, with nothing to compress, there's not much to give. 1/16-1/8 of a turn could start stripping the threads, or put more stress on them than they are designed for.
I may give that a try. I never actually stripped a thread. When I have over tightened the fitting has cracked inline with the tubing from the end through the threading.
 

day_trippr

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The deformability of a nylon flare washer is likely less than that of the PTC connector...

Cheers!
 

jddevinn

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John Guest fittings are also listed as compatible with this tubing. .0025" is well within the manufacturing tolerance of both the tube and the fitting. This is not an instance of misapplied fittings.
 

Mtrhdltd

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This is kind of off topic, tractor trailers use the same type of fittings for air hose connections and they always leak. I was always afraid of converting for this reason. I will keep my stainless ffl fittings.
 

jddevinn

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Not as dangerous as you think. They have an onboard compressor for the air brake system and at least two gauges on the dash showing air pressure. If they start to loose air pressure they know.
 

Deadalus

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John Guest fittings are also listed as compatible with this tubing. .0025" is well within the manufacturing tolerance of both the tube and the fitting. This is not an instance of misapplied fittings.
That's not a particularly strong source regarding compatability, not that I disagree with you.
 

Gozie Boy

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Yes, you are 100% correct that typical "bare" MFL/FFL connections (not "tipped" QDs) require nylon washers. But Williams does say to use teflon tape. I think I will try the nylon washer first (which should be the proper design), and if that fails, then try some teflon tape.
 

tracer bullet

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If these things are all plastic, and hopefully with a flare shape built in if they're specific to the flared fittings, then perhaps the thread tape will help. It seems it could act as its own washer since it's plastic to start with.

FYI for leaks, pipe dope is really best. Tape as mentioned should be considered more of a lubricant to allow tighter fitment between parts i.e. metal pipes with NPT ends where their threads begin to deform. Pipe dope will fill in any empty spaces and provide a seal even without very much tightening force needed.
 

jddevinn

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I had a fairly massive leak today (loud enough that I could hear the tank discharging and determine the area of the leak quickly) , thankfully I noticed and tracked it down before loosing an entire tank. One of the fittings that has been installed for months started leaking through the mold seam right at the base of the smaller hex.

PXL_20210115_034324334.jpg
Capture.PNG
 

day_trippr

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Lucky you were around for the save :)

Looks like a stress fracture at the back of the threaded section that finally let loose.
Been there/done that - I blew out the back of a 1/4" ffl JG fitting by tightening just a wee bit too much.
Lesson learned - I dialed down the final torque a tad. The other 40-something fittings are still holding true, now 14 months in use.

That said, y'all are making me a bit nervous...

Cheers! (Stop that! :D)
 

franknbeans

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I'm making a list to convert my keezer gas/beer over to this tubing since I need to replace the draft lines anyway (didn't clean them, didn't know any better... 🤦‍♂️) I thought these were pretty cool setups and remind me of paintball air lines that use the same idea. those quick connects never leaked unless the line wasn't cut straight. Now I'm seeing how many people have leaks.. I'm kinda timid about changing the gas side. The paintball connects were all stainless/chrome so at least they never broke like these seem to be. Maybe I'll hold off with the gas side for now.
 
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Jayjay1976

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I ordered the clips linked above, they came in and I installed them on all my DuoTight fittings. Then I rolled up the extras in the little baggy and went to put them in my small parts bin, and was amazed to find an identical bag, half empty, of the exact same clips leftover from my RO filter install! Good information to know!

IF YOU ALREADY HAVE AN RO FILTER, YOU LIKELY ALREADY HAVE THE CLIPS. LOOK BEFORE YOU BUY!
 

jddevinn

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I've found that all of my leaks are from cracks in the fittings. I've had the JG version on my beer side for 7+ years without any leaks. This leads me to think that A) the JG fittings are stronger than the duotight or B) (much more likely) I'm afraid of CO2 leaks and therefore installed the duotight fittings too tightly and cracked or stressed almost every one.

I've ordered some more of both but am thinking my issue was all user error. If you install too tightly they will crack.
 

franknbeans

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No worries, I got ya! I hadn't seen that on the site before, so thank you for sharing.
 

bartichex

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For those who have leaks, could some of this be due to not seating the hose properly in the fitting? It’s not obvious, and a little counter-intuitive, but the hose needs to be pushed all the way in, and then PULLED back out slightly, in order to engage the collar inside the fitting.
 

jddevinn

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Almost all of my leaks in the duotights are coming from the body at the seam under the threads even if there are no visible cracks.

Found this one today, the line is going to a fermenter and is at 2.5psi. Marking the leak location and removing to inspect there are no visible cracks. Just leaking at the seam. JG are thicker in this location but I'm still waiting on my shipment of them to try on the CO2 side (I've had on the beer side for 7+ years with no issue.) If they don't work better I'm going back to barbs on the CO2 side and forcing the new lines over them.

PXL_20210121_222414311.jpg
 

jddevinn

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I promise you all the leaks are due to initial overtightening, later manifesting in stress cracks. Keg lube on the threads and flare tip. Hand tight. Pressurize and look for leaks. If it bubbles, one more 8th turn.
I think so too. But I think it is so easy to overtighten because the material is so thin in this area
 

tracer bullet

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Random FYI on clamping EVA Barrier tubing to barbs with oetiker clamps:

6mm tube on a 5/16" barb - 11.3 oetiker is just a bit too small, 12.6 fits perfectly
6mm on 1/4" barb - 10.5 just fits, 11.3 is perfect
5mm on 1/4" barb - 10.5 was ideal

These were the #'s on my clamps anyhow, it seems there's a ton out there w/ slightly different numbers.

Hope that helps someone some day.
 

gnef

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For those using Bev Seal Ultra, John Guest has brass fittings (they are only offered in 1/4" OD and 3/8" OD, IIRC). I've been using 3/8" OD tubing for both gas and beer for many years now. I had been using the acetal John Guest fittings for both gas and beer for many years, and have had a couple failures due to overtightening.

For my gas lines though, I've been changing them over to the brass versions. They are more expensive, but much more durable. I also use these in conjunction with the check valves that go from 1/4" NPT to 1/4" MFL, and use the nylon washer there. I think these are great for the gas side, though I would be nervous about using them on the beer side, so I've kept the beer side with the acetal. I can post pictures if anyone is interested.
 

day_trippr

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Or...just don't overtighten the fittings - and perhaps avoid Duotight 1/4" FFL connectors outright.
I know you have like 16 tapped kegs and countless (50-60?) more presumably on gas. That's a lot of fittings to spend "brass money" on.

I have a total of 61 1/4" FFL to 8mm OD connectors on just my gas and keg purge systems. All but five of them are JG. No issues after now 14 months in service...

Cheers!
 

gnef

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Or...just don't overtighten the fittings - and perhaps avoid Duotight 1/4" FFL connectors outright.
I know you have like 16 tapped kegs and countless (50-60?) more presumably on gas. That's a lot of fittings to spend "brass money" on.

I have a total of 61 1/4" FFL to 8mm OD connectors on just my gas and keg purge systems. All but five of them are JG. No issues after now 14 months in service...

Cheers!
Haha, you have a good memory! It is actually only 14 taps on the walk-in. What's crazy, is that amazon's algorithm changed the price one night at like 2am for the packs of 10 of those brass fittings from $45 to about $10, and I bought 4 packs or so (I really should've bought as many as they had available!), so it wasn't too expensive, but I do intend on eventually spending the money to finish out the upgrade for the gas lines. These brass versions are so much more durable.

I've got the manifolds and secondary regulators in the walk-in, but I also have a number of other regulators, manifolds, fittings, etc. so it is a lot of fittings overall, and the reason why I haven't changed over all my gas lines yet - there always seem to be something else more important to spend the money on at the time! Soon though...
 

day_trippr

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Serendipity can be awesome, but it's an unreliable paradigm :)
btw - what type of tubing are you using? I'm not seeing any 1/4" FFL to 8mm OD fittings in brass, so I'm guessing you're not using EVABarrier on your gas side yet.

Anyway...even if available, at the apparent regular price of around $5 a pop I'd be looking at $300 for brass connectors.
Hahahahaha! Nope :)

Cheers
 

gnef

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Serendipity can be awesome, but it's an unreliable paradigm :)
btw - what type of tubing are you using? I'm not seeing any 1/4" FFL to 8mm OD fittings in brass, so I'm guessing you're not using EVABarrier on your gas side yet.

Anyway...even if available, at the apparent regular price of around $5 a pop I'd be looking at $300 for brass connectors.
Hahahahaha! Nope :)

Cheers
Yup, that's why I had said for those using Bev Seal Ultra. I am using their 1/4" ID x 3/8" OD tubing (I also use 650ss flow control faucets for the added restriction, I have a bit of a unique setup).

They are definitely pricey at full price! I will say that once I realized that I needed more, I kept the amazon page up on a tab for months hoping they would randomly drop the price again... it never happened. haha. They really are great to work with though.
 

day_trippr

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PSA: Do not try to use a hard plastic 8mm OD plug (Duotight) on a 5/16" OD fitting (John Guest). You'll be lucky to ever get that plug out of the socket, and even if you do you'll probably wonder if the socket was damaged and likely replace it on GPs like I just did.

Don't do that...

Cheers!
 

jddevinn

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I continue to have the fittings fail, in areas that I have't touched lately. I know that the failures are due to over tightening, however, I've had ones fail on quick disconnects that I never use a wrench on. Interestingly the ones that are failing with micro cracks..... I can install on beer lines (just for testing) and they do not leak. I've started to just replace the CO2 side with regular MFL -> barbs.
PXL_20210130_005345021.jpg

PXL_20210129_235302240.jpg
 

day_trippr

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Right. It's pretty obvious to me that Duotight 1/4" FFL connectors have a design flaw in the mold geometry that leaves them vulnerable to "excessive" torque - the threshold of which may not be easily determined. I think @Bobby_M's advice to lube the QD (or manifold or shut-off valve) threads and tip, hand-tightening followed by an immersion test, with just slight additional wrench-assisted twist applied should the fitting leak, is good advice, as it will help get to the "just tight enough" state. Hopefully they don't fail after that careful installation...

Cheers!
 
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