Looking for advice - Lots of space under my false bottom

I have a 20 gallon PolarWare brew kettle that I use as my MLT in a HERMS setup. I have a false bottom that has ~ 3 gallons of space under it. I have a feeling that this may be the cause of some of my efficiency and attenuation problems that I've had since I started using this system.

So when determining the volume of strike water - I first start off with 3 gallons (plus the small amount of volume of water that would be running thru the HERMS and then I've done everything from 1.25 qts/lb to 1.5 qts/lb in addition.

So I'm a little concerned with so much water needed for the strike (and less left for the sparge) but then the logical side of me is saying "it shouldn't matter if that water is constantly flowing thru the grainbed and washing the grains".

Today - I decided to switch from fly sparging to batch sparging as I've read a lot of people (even with HERMS systems do this). Unfortunately I picked a "big beer" with 31# of grain (for a 10 gallon batch). So after I drained the MLT into the BK - I was already at 10 gallons. My target was 15 gallons leaving me with only 5 gallons to sparge with. Considering the fact that 3 gallons is under the false bottom I immediately realized I had a problem.

SO this brings my to the point of my question.... Has anyone ever put some kind of "filler" under the false bottom to reduce the amount of space under there? I can't lower the false bottom because of where the ball valve is mounted - it's sitting right on top of the nut - so that isn't an option. I was thinking that if I was able to put something in there to fill a lot of this space that maybe this might help.

Does this make sense? Or am I barking up the wrong tree? If it does make sense to reduce this area - any suggestions as to what to use? Ideally - i'd like to get a bunch of stainless steel marbles but I don't think that would be cost effective (if I could even get them).

Any suggestions or ideas would be greatly appreciated

 

Maybe you could consider a domed false bottom that would significantly reduce the dead space. It could be a little smaller than MLT diameter and be held in place against the bottom via a rigid SS dip tube & clamp.

 

I have about a gallon under my false bottom, and all I do is add it to my strike water. As long as you have a pickup tube and your not leaving alot of wort in the pot that contains sugar you should be good..
What kind of efficiency are you getting when you fly sparge?

 

I'd be a lot more comfortable if all I had was 1 gallon - I think that 3 gallons is excessive. Regarding my efficiency - my overall efficiency is a little under 70%.

I do have a pickup tube that gets pretty close to the bottom.

 

I have a 10-gal MLT with a 2-gallon deadspace underneath which I use to collect 6.5-7 gallons on brew day. I pretty much do it the same way you do - 1.25qts/lb plus 2 gallons for the strike. You're right, proportionally you're going to use less water in the sparge vs. the mash, but last weekend I hit an 85% with a session beer I did, so I don't think it's a problem, at least not for me.

I don't know if this is necessary, but I do a lot of recirculating before I start fly sparging - more even than is necessary for clarity's sake. I don't have a recirc pump yet, but I fill a quart jar with the first runnings, pour it back on top, and repeat that 8 times, so essentially I'm recirculating the entire volume of the deadspace before I start wort collection. Whether it's true or not, in my mind it's removing the uncertainty of the concentration of the dead space and getting the high-concentration wort down close to the valve so when you start wort collection it's not really much different than a no-deadspace sparge.

FWIW, I tried to batch sparge with this same setup and discovered the same thing you did. I tried to mitigate by only partially drawing the 1st running (leaving the deadspace full), pouring in the sparge, and then draining. My efficiency was only 67% but I'm not ready to say that technique was the problem - in retrospect it was probably a combination of a bad crush and a short (45 min) mash due to a miscalculation. If I were curious I'd try it again...but I like beer more than I like science.