Yeah that would help. There is something at the top which isn't labelled on the drawing - I guess thats a release valve?
I suppose you mean for adding dry hops? Sorry if this is a dumb question... but could I just add the dry hops before filling the thing - thru the hatch at the front before I seal it??
Yes, that unlabeled object should be a PRV
Dry hop before knocking out into the tank? Yes. However there are upsides and downsides to consider; obviously dumping them in through the manway is the easiest way to go. If you fill the tank through the bottom valve you will get an almost instant hydration of the pellets, they get mixed into the beer well and drop out easily along with the yeast. Because the aromatic compounds are so volatile, you would have to increase your dry hopping amount somewhat to compensate. On the other hand, post ferment you don't loose any of the aromatics from the blow off, but there is the longer turn around time, more potential for "grassy" character and the possibility that the pellets will clog stuff up. I had a 20bbl uni that I dry hopped get clogged in a BIG way... dry hopped through the top, pellets dropped in and blocked the lower out, some unhydrated pellets also go into the racking arm. What a PITA! It took a LOT of CO2 pressure pushing through those ports to free them up. This was a VERY unusual incident, and my boss at the time said thet in several years and 5 other company breweries, it was the first time he knew of it happening. So, rare, but it can happen.
It's sort of a balancing act, you get a shorter turn around because you have the hops in contact sooner and the instant hydration and currents during fermentation seem to bring the character out quicker. The blowoff loses some aromatics, but it also seems to eliminate the "grassy" character that people sometimes complain about with dry hopping. You use more hops, but you get a shorter turn around and (IMO) a better flavor. Having dry hopped in unis both pre and post ferment, I prefer pre.
Between the two tank options, I especially liked the fact that #2 clearly has a rotating racking arm, whereas #1 seemed to be stationary. If either tank can be used with a spundig valve, that would be awesome.
