The fermenter I installed a couple of weeks ago was leaking coolant. Not a lot, but every little bit matters.
After careful examination, I was able to narrow the leak down to which fitting it was: All of them! Our local plumbing/electrical place carries some Made in Vietnam SS threaded plumbing fittings. They're a biatch to get to seal. I think part of the problem is that the very hard SS threads aren't conformable--they don't deform on tightening--and they're being threaded to equally hard SS ports on the ferm.
I spent far too long getting the glycol coolant drained and getting the thickest pipe dope I have worked deep into the threads. I seem to have gotten it--but it wasn't leaking immediately after I put it together the first time, either. Fingers crossed.
I also realized that I appeared to have been drinking heavily (I wasn't) when I installed the ferm the first time around. For reasons unknown, I had the solenoid valve in entirely the wrong place--in between two of the three cooling jackets. The problem with that is that the solenoid opens and closes FAST, causing a hydraulic shock upstream of it. With a flex line to absorb the shock, it's not a problem. When the valve is mounted directly to the fermenter, it would eventually cause the welds of a jacket to fail.
This is the proper way to plumb it:
Coolant enters through the solenoid valve at the top of the jackets and exits the bottom.
Now to check and make sure I didn't install the valve backwards again.