On drain valves in a tall column...

[indyspirits]

We're getting a new 16 tray column and have been mulling the merits of various approaches to tray draining.  The column will be about 18' tall.  Each tray will have a CIP ball w/ checkvalve.  

Does everyone drain their trays after a run? We always have, but I only have logic and anecdotal evidence that it's necessary.  I had always assumed there will be tails in the tray juice that I'd like to drain out and throw away.  Never tested not draining after each run. 

Notwithstanding, options for drain valves at which I've arrived:

• Ball valve 
• Pneumatic valve
• No drain valve
• No drain valve / weep hole in tray

We have pneumatic valves in a smaller still and they're a bit of a PITA -- need to run brake-line sized tubing to each valve, control is fidgety, valves are expensive, need a dedicated compressor. HOWEVER, they eliminate the open/close acrobatics and large step-platform or ladder. I'm sure OSHA would have fits with some of the crap we've pulled opening valves.

I thought about just saying screw it and have a weep hole (or holes) drilled into each tray. Which would serve to drain trays but the downside is if for any reason you stopped mid run the trays would (obviously) drain.

I dont think the no valve is a reasonable option, but it is an option.

Thoughts / opinions / current practices?