I am looking at modifying the FB. (Moved my thread to equipment forum)
https://www.homebrewtalk.com/f11/modify-false-bottom-355317/
I would love feedback on this. Anyone see issues?
I wouldn't bother with screwing around with the false bottom.
I brew 5 gallon batches in a 10 gallon Polarware kettle which has a similar fitting/false bottom set up to the B3 kettle you have. I had the same issues you are dealing with...1) a ton of volume under the false bottom which made mashes too thick and 2) a ton of dead space under the outlet on the kettle that left quality wort behind.
The solution for both starts with a 1/2" stainless steel street elbow. Don't bother with the fancy dip tubes. The Polarware kettle allowed just enough room for me to screw it into the female thread side of the output port. As long as you have a tube coming off of the valve that will allow a siphon when draining, the street 90 will pull almost every last drop off the bottom of the kettle. The street 90 is full port, cheap, and has no moving parts. That special Male X Female fitting that Polarware and B3 use on their kettles is practically begging for a 1/2" street 90.
The second problem you are having is that you are overconcerned with a water:grain ratio, and all of the deadspace under the false bottom is not allowing enough water to properly mash the grains.
I'll give you my system, and you can consider if it will work for you.
Upon receiving my kettle, I filled the tun with water to the point that the water level met the peak of false bottom. Then I measured out 5 gallons of water above the level of the false bottom, and I use a marked measuring stick for repeatability.
Every batch, regardless of gravity, gets mashed with 5 gallons of water...I know, weird. I got that tip from Mike McDole on a podcast - he uses 9 gallons of mash water for every batch (but he makes 10 gallon batches). I like 5 gallons because it is an easy measurement to remember, doesn't make low gravity mashes too thin, and doesn't make high gravity batches too thick.
Meanwhile, I heat 8 gallons in my hot liquor tank to be used for my HERMS coil and later for sparge water.
High gravity batches will absorb more water into the grain and will require more sparge water. Lower gravity batches will absorb less water and will require less sparge water. I always collect 8 gallons of wort for a 5 gallon batch. Doing the math, a low gravity beer may only use a couple gallons of sparge water, and a high gravity batch may use a few gallons. I always target 70% efficiency, and I do not want it to be any higher. Once I have 8 gallons of wort in the kettle, I close off the valves, and use of the remaining sparge water for cleaning.
I like this method because it makes water chemistry and the brew process consistent. I know it is a little mindblowing to abandon the water:grain ratio, but I suggest you give it a try.
