Locknut not water tight. Epoxy/caulking?

I am building an e-keggle. Just finished soldering (silver solder) the locknut for my element. It's not completely sealed. There is a small area on the top that appears to be wet, even when blowdried. I have already resoldered twice. The same area will not completely seal. Can I caulk or epoxy it?

 

If you're not sure, try filling with water and see if it leaks. It could be just flux giving a wet appearance. If it does indeed leak, heat it up and try soldering again. Don't be dismayed, you can do it!

 

John, it doesn't drip, just looks wet. I blowdried it to see whether it would evaporate and it did not.

 

Dry it, clean it (MEK works best, yes it's nasty stuff) reflux then re sweat it. I have done some a couple times.

 

If you had flux on your mating surfaces, heated until the flux started to bubble and flow, then touched on the silver solder. The solder will follow where there is flux, so long as the heat is there. A perfect joint will have very little solder visible since it should be between the two mating surfaces.
You can buff out or lightly sand off any residue if you want a cleaner looking joint.
To check the joint, fill your keg wth water so there is pressure on the inside of the soldered joint. Put soapy water around the joint on the outside. If bubbles appear, then your joint is leaking and you need to try again.
Hope this helps.

 

could be flux?

 

I just put a little extra silver on with flux and resoldered the one area. Completely sealed now, hopefully not a weak joint.

 

A picture would help. There is no way the solder would stay wet. If it's not leaking, you are fine. However, what is the plan for grounding and protecting the wiring?