How much of a gap for false bottom?

I am trying to use a penrose kettle for a direct fired mash tun. It has a diameter of 15.75". I see plenty of 15" false bottoms available. That leaves a difference of .75" or .375" between the edge of the false bottom and the sidewall of the pot. Is this too much? It seems like it is but I wanted to get others opinions. I know there is probably some gap between the edge of the false bottom and the sidewall of the pot that it fits in but this seems like it would be too big and a lot of grain would get through.

Another question is how much space should be between the bottom of the mash tun and the false bottom? I Know I need to be above the outlet or have some plumbing to a dip tube. Is there an advantage to having more or less space if I am doing a direct fire re-circulation?


Anyone in the Los Angeles area with some metal working skills feel like making a 15.75" false bottom?

3/8" it too big. Does primrose not offer a false bottom? Look for Jaybird on the forum. He is a vendor and makes very nice custom false bottoms.

I was just going to solder up some copper pipe to make mine. Make a ring with a cross through the center. Cut Slots in the bottom of copper tubing and screw it into the 1/2 in threaded fitting. Figured it would be much like a cooler with PVC pipe.

If you direct fire, you can't really have a manifold laying on the bottom. Any bits of grain that get held to the bottom will burn.

You can take up some of the gap between a false bottom and the tun sidewalls by taking a length of silicone tubing (say 1/2" OD x 1/4" ID) and slitting it long ways to fit around the edges.

Zeal said:

I was just going to solder up some copper pipe to make mine. Make a ring with a cross through the center. Cut Slots in the bottom of copper tubing and screw it into the 1/2 in threaded fitting. Figured it would be much like a cooler with PVC pipe.

Click to expand...

I went this route when I started to do all-grain and I can guarantee that after you see sub-par efficiency and your manifold get's all bent and deformed from getting banged around you'll switch to a false bottom too. If you're going to direct fire the mash a false bottom is the way to do it.

Bobby_M said:

If you direct fire, you can't really have a manifold laying on the bottom. Any bits of grain that get held to the bottom will burn.

You can take up some of the gap between a false bottom and the tun sidewalls by taking a length of silicone tubing (say 1/2" OD x 1/4" ID) and slitting it long ways to fit around the edges.

Click to expand...

Silicone tubing is a great idea! I would also get a very good seal that way.

I talked with Jay already - I'm sure it's a very nice false bottom but it's almost the price of the pot. He did have a hop block that might work.

I'm also considering the blichman false bottom for the 15 gallon pot - from what I gather it is 15.7" which should fit fine. I would just need to put a stand on the bottom.

oops