20 gal plastic drums - airlock & valve config?

I just got 2 of these 20 gallon plastic drums from ebay.

They have these clamp on lids


Smelled to all hell like olives when I got them, but a 3hr soak in hotwater & oxy took care of that.

I'm trying to determine how to rig an airlock or blowoff and whether or not I want to install a drain valve or not.
I know I could just drill a hole and jamb an airlock in it, but whatever I do, I'd like to be able to cap off later. That's why I'm kind of thinking a weldless bulkhead through the lid to a blowoff tube might be better. That way I could just put a 1/2" NPT cap on it.
*Think a 1/2" opening is adequate for a blowoff?
*What size hose would be minimum?

I know if I add a spigot, I still won't be able to drop out sediment like a conical. It would be nice to be able to take samples, though and maybe for racking, but do you think it would be worth the added hassel of disassembly and cleaning... or should I just abandon it and stick w/ an autosiphon?

You could use a PVC threaded union for the nipple and attach large OD/ID vinyl tubing akin to what is used for pool supply runs. Allows you to use 1" or larger tubing then.

Funny enough I've toyed with the idea of using drums like that for both MLT and fermenter. I second the use of the pvc fittings. Even for your drain, the bulkheads will probably let you crank them tight enough to flatten the drum where the bulkhead is for a sure seal. They also make things called uniseals that work well on round shapes, google for them. Once you have pvc, you can do more or less anything you want. I'd be really curious as to how well they work out. I'm trying to save for a conical but I can buy a 55 gallon drum for $75, was toying with the idea of using a pair until I can get the conical.

If you have a farm supply store or well equipped hardware store, you can usually find bulkhead fittings, in the area where sprayers & pumps are.
http://www.plumbingsupply.com/bulkhead.html

I added a grommet for the airlock and the better bottle racking arm and valve, I can drain it so that I only leave a cup or two of wort.
You could just drill a larger hole and get one drilled stopper and one solid stopper, or just make the hole in the lid exactly the size of the large blow off tubing and buy the stoppers sized to that for your airlock and plug.

I might have to score a couple of them for grain storage.

You don't need to bother fitting an airlock on it. I use one of those as my primary when I do 10 gallon batches and I just leave the cover on with the band in place but not clamped down when the vigourous fermentation is going on. After a few days I clamp the lid down. The pressure never becomes an issue. I'll generally rack into glass after a week but I've left lagers in there as long as a month without a problem.

I know this was an old thread. I'm new to large batch brewing. Anyone got any improvements or better ideas than this one out there let me know. Works well and its cheep. This was someone else's design I found.
My drum lids have 2" NPT bungs in them. As most do. So I wanted something easy to slap on them. So I went and picked up a package of 6 ping pong balls. $3 at K Mart. Then headed to Lowes armed with a ping pong ball. Was rummaging through the PVC fitting isle. Grabbed a male 2" NPT adapter. And looked for something to fit the ping pong ball. And I found it. A 2" X 1 1/4" reducer bushing. The ping pong ball fits in the 1 1/4" female section with air space on the sides. And a lip to hold it up and seal against it. I think both fittings were $3. So $3.50 for each airlock.

Parts list.
Ping pong ball.
2" male NPT adapter PVC.
2" X 1 1/4" reducer bushing PVC.

Glue the two together. Or press fit would work. Screw it into the drum bung. And drop the ping pong ball into place.

https://www.youtube.com/watch?v=IUjHqj_8ce4