Duotight and CO2: Hand-Tight not Enough?

[Clint Yeastwood]

Am I the only one who gets bad results with Kegland's instructions for screwing on Duotight connectors?

In their video, they just screw them onto MFL fittings by hand, and that's that. I also read I was supposed to screw them on hand-tight and then go 1/4 turn. In reality, I have to go maybe 1.5 turns past hand-tight to get the bubbles to stop. After that, everything is fine.

Moved the CO2 in my keezer to Duotight and EVAbarrier last night, and I lost quite a bit of CO2 to a loose Duotight. I checked the fittings for leaks when I installed them, but I believe the solution I used (Star San) was not bubbly enough to reveal everything. I omitted the nylon washers suggested by a nutty website (tried that before and ruined a couple of fittings) and used Teflon to cut friction. I think plain old keg lube or Super Lube would work just as well. I went hand-tight plus 1/4 and then used the Star San solution to check for bubbles. Things looked good, but then my CO2 tank pressure dropped.

Tonight I got out some solution made with Dawn and applied the wrench. All is fine now. I think.

Seems it would be useful to come up with a guaranteed method in order to help others avoid losing CO2 in the future. The way I did it tonight seems to have gotten the job done.

 

[wepeeler]

I've had pretty good luck with everything Duotight. I tighten by hand and then use a wrench to apply a touch more pressure, without feeling like I'm going to snap them. Never had a leak, that I'm aware of.

 

[whoaru99]

Moved the CO2 in my keezer to Duotight and EVAbarrier last night, and I lost quite a bit of CO2 to a loose Duotight. I checked the fittings for leaks when I installed them, but I believe the solution I used (Star San) was not bubbly enough to reveal everything. I omitted the nylon washers suggested by a nutty website (tried that before and ruined a couple of fittings) and used Teflon to cut friction. I think plain old keg lube or Super Lube would work just as well. I went hand-tight plus 1/4 and then used the Star San solution to check for bubbles. Things looked good, but then my CO2 tank pressure dropped.

If you get bubbles, OK, that's sign of leaking and checking with soapy water (etc.) is as close to a guarantee as you're going to get.

That said, when a CO2 cylinder moves from a warmer place into a colder place (like into the keezer) the pressure WILL drop even with no leaks. This is normal, not inherently sign of a leak.

For example: CO2 at 70F = ~850psi. CO2 at 45F = ~610 psi.

Sticking with the example (and presuming there is some liquid CO2 in the tank) the pressure will go back to ~850psi if you take the cylinder out of the keezer and allow it to come back to 70F.

 

[Clint Yeastwood]

The tank was not moved.

 

[whoaru99]

Ahhh.. OK. By moved it means changed the connection styles. Got it.

 

[Broken Crow]

I doubt this is your problem, but just to eliminate the possibility: Did you rinse the Star San off? Duotight fittings are well known to break down when soaked in Star San.
Dunno how it works for others, but when I install a Duotight to the MFL on my regulator, I need about a 3/4" turn past hand-tight. My own next upgrade to my gas lines will be to use the 1/4"ID Evabarrier swaged over SS swivel-nuts.

 

[BongoYodeler]

I tighten mine hand-tight plus a quarter turn with a wrench. I have never had one leak or break.

 

[Clint Yeastwood]

I can't blame Star San damage because this was a new fitting. I think Star San just isn't foamy enough to trust for leak checks. I trusted it, but it didn't show me a leak that was very obvious with Dawn.

As for technique, I feel like the answer is to get out a spray bottle of soapy water or a bucket you can sink your fitting in, tighten it just enough to stop the leaks at very high pressure, turn the pressure down, and hope for the best. I used a little Teflon this time. I think I'll go for keg lube or Super Lube in the future, depending on which one is closest to the keezer.

Anyway, I'm all set until the next time I decide to change a fitting.

 

[DuncB]

Agree with you about immersion the best test.
Allegedly new plastic formulation for duotight not as vulnerable to Starsan spray and then dry. But why take the chance.
I think finding that sweet spot of tight enough but not too tight to cause failure is tricky.
I had a leaking duotight ball lock on the gas side that needed an Oring fitted never had this problem with other ball lock connectors.