Keg still questions - Safe volume space - drain parts?

[TheRedDawg]

Getting back into the sport after being gone for a couple of years. Upgrading to a stainless keg still. Prior I used a 10 gallon (38 liter?) stainless pot with a homemade lid. It worked but was a pain to seal when distilling. I’ll preface all this by saying I typically do a sweet feed mash. Simple and straightforward. I’ve done some oaking but mainly cut with spring water to make apple pie or lemon drop or creamsicle. Straight run makes a fine margarita too. But I digress. Back on topic…

2 questions:
1. How much headspace do I leave in a pot still when I add in the wash for distilling? Probably a loaded question depending on variables. It’s those variables I’m interested in. See below for details of my rig build. Long ago, I think I read it was like 80% capacity of the container?

I “think” my keg is 15 gallons capacity. I got this putting a stick into the keg, marking it and measuring the depth (~22 inches). Then I measured the distance across the top (~ 14 inches ). Using an online volume calculator, it came back with 14.66 gallons. I will eventually fill up the keg with water and siphon into 5 gallon buckets to get a more accurate measurement.

2. Drain questions: what size drain and what parts? I’m going to want to put a drain at the bottom in the side. Have a friend who’s a welder. It’s going to be all stainless parts. Question is what size? 1/2” , 3/4”, 1”? What’s normal? No. I do not want to cut the top and flip it over at this time. Plans are to put a drain on the side near the bottom. I’ll place the drain so the keg can sit safely on my burner. Yes, I’m going to use propane for now. Later I may go electric but that’s down the road.

See below for a pic of what I am converting to. Nothing new (but new to me). Basically a keg with a 2”x12” tri clamp sitting on a custom made propane stand. Eventually, I’ll add in a thumper. Had great luck with that on my previous still