Silicone gasket on the inside or outside of a weldless fitting

[JayMac]

Hey everyone,

I've looked at dozens of articles explaining how to install weldless bulkhead fittings. They are simple enough, but the one thing I'm stuck with, is that half of them say the gasket should be placed on the inside, while the other half say it should go on the outside. I know Bobby advocates the gaskets on the outside, and believes the contrary is a leading cause of leaks.

However, the fact still remains that there are still two opinions on this matter. I was hoping that we could figure this out, once and for all.

Which side should be silicone gasket go on, and why?

To me, the inside seems most logical. Although I haven't tried it, it seems to make the most sense that the crushing between the interior wall and the locknut, coupled with the pressure exerted by the water/wort would cause the best seal. But as I said, I've never tried it, so I'm interested to see peoples opinions and to see if there is actually a general consensus.

 

[barrooze]

Both!

No, really, if you have an o-ring on the inside that's food grade, it'll be fine. The liquid inside the vessel will keep the temps the o-ring experiences to boiling temps. The o-ring on the outside of the vessel doesn't have any additional buffer to the heat, and if the vessel is on a flame, the o-ring can experience temps much higher than boiling. Silicon has a much higher max temp limit and for that reason is recommended for the outside of the vessel.

Since they're fairly inexpensive, I used silicon on both the inside and outside of my boil kettle.

 

[OKHopHead]

Normally, you would want the pressure inside the vessel to aid in creating a seal. This would indicate placement of the gasket on the inside. However, in this case we are only dealing with about 1 psig (p=h*0.434*SG) inside the typical kettle. Probably not enough to have much of an effect.

If you are using a washer as opposed to an o-ring, the curvature of the kettle will have an effect. On the outside, the most compression will occur along the inner circumference of the washer. On the inside, the most compression will occur along the outer circumference of the washer. This will require more deformation of the washer to create a proper seal. Again, the effect here is minimal and a proper seal can probably be obtained either way.

I agree with barrooze that a gasket outside could experience higher temps than a gasket on the inside. My vote would go for placing the gasket on the inside.

 

[tre9er]

Does your locknut have a groove to seat on the o-ring? If not, you may prefer one that does, like from Bargain Fittings. That helps from squashing the o-ring in an uneven fashion that can cause leaks. I put all mine on the inside as they are BF kits with grooved locknuts. Hand-tighten, never had leaks. You can bead some silicone sealant around the hole before final assembly, too...just for good measure.

 

[BargainFittings]

Our standard kit has the fully machined grooved locknut that has been designed to properly seat the o-ring.
We've designed our keg diptubes to fit the kits when they are installed as instructed - inside the keg wall.

The locknut o-ring combo will in fact work on either side and will seal fine.

Our new style bulkhead kit has a flat gasket instead of an o-ring and is designed to seal on the outside of the vessel due to the curve of the keg or kettle wall.

 

[tre9er]

Our standard kit has the fully machined grooved locknut that has been designed to properly seat the o-ring.
We've designed our keg diptubes to fit the kits when they are installed as instructed - inside the keg wall.

The locknut o-ring combo will in fact work on either side and will seal fine.

Our new style bulkhead kit has a flat gasket instead of an o-ring and is designed to seal on the outside of the vessel due to the curve of the keg or kettle wall.

I use all of his^ stuff. Probably dropped a few hundred in SS fittings over the past 6 months :rockin:

 

[JayMac]

I do have grooved SS locknuts, so I'm good! I have silicone O-rings and washers, so I think I'll use them for specific scenarios. For example: for my BK and MLT, I have a female threaded adapter (for diptube and manifold) which I will thread directly onto my nipple. For this scenario, I will use a gasket so there is no uneven seal (as you mentioned tre9er). Then, for all of the fittings on my HLT (thermometer, valve, and sightglass), I will be using O-rings and grooved locknuts. Hopefully I don't have any leaks the first time around.

My SS fittings ship Monday and should be here within a few days afterwards. Never drilled into SS before... so I better not mess up the first time! That's what watching hours of youtube videos in order to prep is for

I guess if I experience any leaks, I'll just dissasemble, and try the O-ring/gasket on the outisde.

 

[tre9er]

Never drilled into SS before... so I better not mess up the first time! That's what watching hours of youtube videos in order to prep is for

I guess if I experience any leaks, I'll just dissasemble, and try the O-ring/gasket on the outisde.

1. Use cutting oil and run the drill slowwww with a lot of pressure.

2. don't overtighten. Not all bulkheads need to be as tight. For instance, the valve on my MLT spins very easily but doesn't leak.