For my newest incarnation of my brewery, I have a 2 vessel system, (15 gal keggle and 15 gal cooler MLT). I am mashing at 1.5 qt/lb in the MLT, then recircing my full boil volume through the MLT/BK. Finally, I pump all the liquid into the BK, (I shut the return to the MLT). So, like jKarp's countertop Brutus 20, but with only 1.5 qt/lb in the MLT, not the full boil volume in recirc during the mash.
When I pump the wort up into the BK, I am draining my mash tun. I'd like to have a way of knowing WHEN that draining is complete, (i.e, when my pump sucks air). It can be a bit noisy in my brewery, so listening for the pump pitch change is tricky.
I figured a clear "sight tube" between MLT and pump would work great. I'll see bubbles going through it, and know I'm done. I know I've seen SOMETHING like this in one of the blingy triclover setups on here a while back.
What's it called? Anyone DIY one? Mine would be with brass QDs from McMaster, not triclovers...
Alternately, anything that functions as a cheap flowmeter would work...something like the whirlygig that used to be on the side of gas pumps?