I working on a new mash tun made from a Sanke keg. The only change from my old mash tun is that I'm raising the false bottom a few inches so the pickup tube and thermometer probe are all underneath the false bottom. This should make stirring easier as I won't hit the thermometer probe and pickup tube while I'm stirring.
I've got everything put together. The only issue is that there is about 2 gallons of volume beneath the false bottom that will fill with wort but not grain. I have a couple questions about this.
A typical 5-gallon batch may require 3 gallons of mash water. If I put 3 gallons of mash water in my mash tun the top of the grain likely won't even get wet. Can I just add 2 gallons to however much mash water I need? Meaning that if I calculate that I need 3 gallons, I can add 5 gallons? Adding 5 gallons would get the right water/grain ratio correct where the grain is in contact with the water. This would also dilute the enzymes. Not sure if that dilution is significant enough to effect conversion.
I have a HERMS so the mash is continuously recirculated. I can work on reducing the volume under the false bottom but am not sure if that is necessary. I understand I won't be able to use as much sparge water but with my HERMS I'm hitting high 80s for efficiency and that's not a big concern.
Another clarification, I do runoff nearly everything from the mash tun including the 2 gallons underneath the false bottom.