is my mash tun too big

[farmbrew]

Hello all, I am going to be jumping up to 10 gallons as soon as the weather warms up and I get the rest of the equipment. My questions is I have a 25 gal megapot, a 15.5 gal converted keg and I want to use the 25 gal for a MT and the 15.5 gal for BK but have been reading that there is too much dead space and maybe not enough of a grain bed depth for fly sparging, which is what I am looking to do. Will I be ok to proceed or should I use the 25 gal for BK and 15.5 gal for MT, if so does using the 25 gal for BK pose any problems. Thanks in advance.

farm

[BDawg]

I'd boil in the big pot and mash in the keg.
LOTS of folks mash in a converted keg with no problems.
They can hold a LOT of grain.

[foomench]

My first reaction was use the big one for the mash tun, and the small for the BK. You can use it for high gravity beers. Just how wide is the megapot?

[Dean Palmer]

I don't think there is a single correct answer, and the best answer will depend on what you are trying to brew on any particular day. With a system that has equally sized vessels, I find myself regularly topping out the capacity for the mash, so the larger vessel would be nice to have for some higher gravity beers using the keg kettle as the BK. If it were a normal gravity beer, I'd prefer to have similar vessels, but mashing in the keg may be sufficient to give you what you need and boiling in a vessel with a lot of excess capacity can be nice.

For a fly sparge when making normal gravity beers you probably won't get a good grain bed in that larger vessel. I'd simply batch sparge when needed. The resulting beer will be the same so no worries there.

The options are really open, and it is nice to have different tools in the box for whatever you want to do.

[captain carrot]

I bought the 20 gal megapot and false bottom from Northern Brewer. The space beneath the false bottom was 3 gallons worth. I was able to shorten the feet on the FB to reduce that to 2 1/2 gallons. If you are using a mesh screen in the megapot you should be fine. If you have a false bottom figure out the volume beneath the perforated FB and determine how much water you will need to get a proper water/grist ratio above it. Batch sparging may be difficult on lower gravity beers. You should be able to mash around 35 lbs of grain in the converted keg. If you want to do 10 gallons of a larger beer than you may want to set your system up so you can switch the 2 vessels. Boil off rate will be greater in the megapot due to its width also. It may take a little more math but you can make this work.
Good Luck!

[farmbrew]

My first reaction was use the big one for the mash tun, and the small for the BK. You can use it for high gravity beers. Just how wide is the megapot?

the megapot is 21 in wide.

i use a custom made copper manifold

thanks guys, i think I will use the 25 gal for a bk, I may boil off a bit more but as mentioned I may switch based on the brewday and I dont' really brew high gravity so the larger mash tun may not have enough depth as i was thinking. Thanks again guys you helped steer me in the right path.

cheers,
farm

[pdbutts]

I think you will be happy with your decision to mash in the keg. When brewing a 12 gallon batch your preboil volume is generally 13 -14 gallons just for a 60 minute boil, bump it to 90minutes and you are just about out of space in a keggle. Also when I brew real high gravity beers that would use more than 17 lb in a 6 gallon batch they are specialty brews (Barley Wine, RIS, Baltic Porter) meant to age for a bit so 6 gallons is pleanty as I am most likely going to bottle, not keg them. 54 bottles is enough bottling for me