DUOTIGHT LEAKS......

[jddevinn]

Coincidentally, I see today (in another, related thread) that it is now being suggested to use teflon tape on the Duotight's ffl connections to SS mfl threads, such as on the MFL outlet of a regulator or distributor (but not needed for plastic-tipped keg QD connectors).

I had always thought that this was not needed, and even Kegland's own video shows them threading the Duotight ffl directly onto a metal mfl-threaded coupling with no teflon tape. Seems like this may apply to my problem, and certainly worth a try.

From Bruce_the_loon:
Poking around on the net a bit has most sites copying the sales blurb from somewhere with a line that there are special instructions for flare fittings which aren't in the blurb.

Williamsbrewing.com has a note that stainless steel MFL connectors will need some teflon tape to make sure the seal is good and has a video which may or may not be relevant.

DuoTight 8mm To Female Flare
Double O ring push fitting fits standard pin lock threaded fittings, and accepts EVABarrier lined tubing.

www.williamsbrewing.com

Hope it helps a bit.

Hmmm. The 'FFL' and 'MFL' are -4 JIC fittings that should not need tape. I put the plastic conical washers that traditional go between the metal FFL and MFL pieces in a couple spots to see if it would help.... it helped me accidentally over tighten but that was it.

For those that have leaks, do you use StarSan and let it stay in contact with the fittings? People have mentioned that StarSan is not good for this type of plastic and can cause cracks. If you do use StarSan, I wonder if there are small cracks on the inside that you haven't noticed.

Hmm. I do for sanitizing and if I have a leak I spray them down to look for bubbles. I did have on leaking right in the middle of the body of one.... ordered some other fluid to use.

 

[tracer bullet]

Is there a size mismatch? I see EVA barrier lines sold in millimeters, and fittings in the US sold in inches. If slightly too small lines are going into the fittings they will indeed leak.

(I've been around some laser welding systems that come from Europe and we swap out their metric fittings with our own so we can keep one standard system of tubing i.e. 1/4" not 5 mm).

 

[ns.88]

Is there a size mismatch? I see EVA barrier lines sold in millimeters, and fittings in the US sold in inches. If slightly too small lines are going into the fittings they will indeed leak.

(I've been around some laser welding systems that come from Europe and we swap out their metric fittings with our own so we can keep one standard system of tubing i.e. 1/4" not 5 mm).

I could be wrong but I was under the impression that the US sellers of Duotight (Morebeer, Williams, etc.) import it from Kegland (or Keglands distributor) so the size of the fittings shouldn't be different in the US.

 

[tracer bullet]

Perhaps, but when I bought my EVA Barrier tubing (Morebeer) it was listed as 4, 5 or 6mm. I shoved it over my existing barbs so I didn't care much. Fittings are normally not metric in the US. Maybe you're right but it could really depend on where one purchases them? Or they do a "close enough" conversion.

Just a thought. If there's a mismatch it could be an issue.

 

[jddevinn]

All of the EVA tubing is 8mm OD, the ID is different. The duotight fittings are for 8mm OD tubing.

 

[tracer bullet]

All of the EVA tubing is 8mm OD, the ID is different. The duotight fittings are for 8mm OD tubing.

I wanted to disbelieve, but there's a lot correct here. Looks like 4 and 5mm tubings are indeed that ID, with 8mm OD. The 6mm (perhaps 6.5, site dependent on what they call it) is a 9.5mm OD. (I'm used to a 1/4" or 5mm tubing being that OD, it's normally how it works, but within the specific duotight system they are indeed using different terminology)

Duotight offers indeed 8mm and 9.5mm fittings, working well for that tubing.

Anyone using other brands of push connect fittings should however take note i.e. if you brought some tubing to Home Depot and got whatever seems to have worked. But most folks probably are not, for this anyhow.

 

[MikeCo]

Williamsbrewing.com has a note that stainless steel MFL connectors will need some teflon tape to make sure the seal is good and has a video which may or may not be relevant.

The product info linked says this. I don't understand it; it sounds contradictory. It says it seals tight without tape, but you should use it?

The fitting seals tight without teflon tape when using plastic ball and pin locks, but you will need to wrap stainless male flare threads is a bit of teflon tape to get them to seal before threading these on.

 

[day_trippr]

It's not contradictory: ball lock and pin lock disconnects sporting 1/4" mfl stems have integrated gaskets at their tips.
Meanwhile, the typical manifold or regulator shutoff valve is naked metal...

Cheers!

 

[tracer bullet]

It's not contradictory: ball lock and pin lock disconnects sporting 1/4" mfl stems have integrated gaskets at their tips.
Meanwhile, the typical manifold or regulator shutoff valve is naked metal...

Cheers!

For which I normally use these. Work great for me. Definitely leaks without them for which I don't think thread tape would help.

Nylon Flare Fitting Washers [Nylon-Flare-Washers] - $0.14 : The Chi-Company, a home brewing company since 1996, New and used beverage equipment for Homebrewing, Home winemaking, Soda systems and used Pepsi vending equipment

 

[h22lude]

Hmm. I do for sanitizing and if I have a leak I spray them down to look for bubbles. I did have on leaking right in the middle of the body of one.... ordered some other fluid to use.

You can use StarSan, just rinse it after. I push it through the lines then hook up all the kegs and pull beer from each tap. Minimal contact time but enough to sanitize.

 

[h22lude]

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]

For which I normally use these. Work great for me. Definitely leaks without them for which I don't think thread tape would help.

Nylon Flare Fitting Washers [Nylon-Flare-Washers] - $0.14 : The Chi-Company, a home brewing company since 1996, New and used beverage equipment for Homebrewing, Home winemaking, Soda systems and used Pepsi vending equipment

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]

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]

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]

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

 

[jddevinn]

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.

 

[Deadalus]

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

John Guest fittings came up in the discussion as well.

 

[day_trippr]

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

Cheers!

 

[jddevinn]

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]

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.

 

[day_trippr]

Holy cow...

 

[jddevinn]

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]

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]

For which I normally use these. Work great for me. Definitely leaks without them for which I don't think thread tape would help.

Nylon Flare Fitting Washers [Nylon-Flare-Washers] - $0.14 : The Chi-Company, a home brewing company since 1996, New and used beverage equipment for Homebrewing, Home winemaking, Soda systems and used Pepsi vending equipment

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]

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.

 

[pvpeacock]

Here they are:

https://www.amazon.com/gp/product/B00YGR576K
They work great

Do these work for the Duotight fittings?

 

[marc1]

Do these work for the Duotight fittings?

Yes - I've got them on mine

 

[jddevinn]

I've ordered the same ones and will have on mine by next week

 

[jddevinn]

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.

 

[day_trippr]

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! )