Everything is screwed on. I don't know what hardware stores you have there but Orchard Supply Hardware has NPT (National Pipe Thread) nuts so you can use a nut on galvanized pipe. So for the heating elements I just got 1" pipe thread nuts and cut a hole and used a bunch of (the red sealant) red sealant from the auto store, I had it lying around, but it's the best. It's High Temp Silicone Sealant, works like a charm.
First thing I did was layout where the legs of the keg were going to sit, the keg is about 9" of the bottom, I could have made it closer but the garbage can is so tall why make it tight. Anyway the keg is about 9" above the bottom to clear the heating elements and ball valve. Oh, I'm sure the ball valve would be able to turn without messing anything up but I already had a cheap one that was not too tight, some of the plastic ball valves for PVC or quick disconnect at home depot are hard to turn and I wouldn't use them. For mine I'm still going to grab the housing before turning just to be safe. The best part is not matter if it leaks a little the garbage can, same type I've used to hold water in other projects, won't collapse or blow out. Where was I, oh yes, layout where the risers go then drill opposing holes for the heating elements and the ball valve opposite of those. Then I rough up the hole inside and out with sand paper and wipe it down with a dry paper towel. Then I use a wire brush and acetone, because acetone will evaporate immediately and is the only solvent that won't leave behind a reside, to clean all the grease off the metal parts. Then I use the sealant in gobs. First I smear a little on the inside, outside and rim of the hole, working it in for good contact and then put a bead on the element and work it into the threads. Then push it through the hole. Then I put a bead on the nut and screw it on. I have a special water heater element socket, so that and a large adjustable wrench on the inside and make sure it's pretty tight, not SUPER tight as you're tightening against plastic. Then I put a bead on the inside and outside and make a nice dam. Then I use a flashlight and a mirror on the inside to make sure the underside of the nut, I can't see, has a nice smoothed bead on it.
I then hot glued the cord in place for the water pump.
As for the keg, it's a ton of work. First I had to cut out the center pumpkin of the keg, grind that edge down to where the keg was welded to the top rim. That took 2-3 hours with a grinder. Then I had to MIG and TIG weld the weep holes and weld on pieces of SS to where the handles were. This wasn't necessary but I wanted one solid vessel where no bacteria could live and give me the extra head space I want so I'm not pushing the limits.
The problem is once I welded the vessel there was splatter and I was so much in a hurry I forgot to either spray it will weld release (splatter guard) or cover it. SO the first time I filled it overnight to check for leaks there were little specs everywhere of rust. For those of you who don't know metallurgy Stainless Steel is just steel with extra carbon, so if you over heat the Stainless for too long it becomes steel again, kind of, it will rust is what you should take away. So the weld specs weren't shieldied by gas so they rust. Not a big deal but I had to polish the inside with my roloc discs, back breaking, loud (I always wear hearing protection), and took forever. I also had to fill in some pin holes they weren't leaking but I don't want bacteria in there even though I will sanitize with Star San every time.