You’re ready to take the leap to all grain, and here I will show you step by step how to build a 10 gallon mash tun from a cooler. While you’ve been considering converting to all grain brewing, you (like me) may have been intimidated by the idea of the new equipment required. Hopefully after this post I’ll have you convinced that learning how to make a mash lauter tun is easy to do, and cheap as well. The next post I’ll walk you through the assembly. I’ve done all the research and shopping around for you. The main thing that you need to convert to all grain brewing is a vessel to hold all the grain while you do the mash, and then something to let you drain away the sweet wort and leave the grain behind. This project was by no means my own idea–it is mentioned in many places, including John Palmer’s book How To Brew in the appendix, and online in the HomeBrewTalk forums. I thought I could make a few things a little clearer in some areas to make it as easy for you to do this yourself as possible. One quick thing you should know – it really is worth it to build a 10 gallon mash tun rather than building a 5 gallon one, although these parts will work for both. I’ve put in two options for the build: one with a false bottom you build from a braided stainless hose, and one with a pre-fab false bottom for purchase. Let’s get shopping!
I chose to design mine with a circular “false bottom” to work as the filter, made from stainless steel braid taken from a faucet supply line. Other designs have a simple straight piece rather than doing the circle. In my reading & research I found that the circular design provides better draining, less likelihood of a stuck sparge, and it better distributes the weight of the grain when the cooler is full.
Shopping list (by store name, updated most prices as of Feb 2013):
Home Depot or Lowes (see picture to right):
- 10 Gallon Picnic Cooler ($45) – I got a 10 gallon Igloo on Craigslist for $25. Rubbermaid is another brand.
- Get 2 of the: Watts A-298 (part number, in plumbing section) – Hose Barb Adapter – 3/8″ Barb x 3/8″ FIP (female) – $3.40 ea
- Watts A-294 – Hose Barb Adapter – 3/8″ Barb x 3/8″ MIP (male) – $3.12
- Watts A-786 – Brass Pipe Nipple – 3/8″ MIP x 1-1/2″ – $3.40 – in later pictures – the piece that passes through the hole where the spigot is removed from the cooler.
- Watts A-168 – Flare to Flare to Flare Tee – All 3/8″ – $5.11 – second from left of picture
- Watts A-760 – Coupling 3/8″ FIP – $4.47 – far left of picture
- 3/8” threaded ball valve – $8.21 – with red handle in picture
- 30″ Stainless Steel faucet supply line 1/2″ diameter – $8.49 – I actually got the guys at Home Depot to cut the ends of this off for me with a hack saw since I don’t own one myself and you need to do this for the project.
- 4 x 5/8” fender washers (or flat washers) – $.35 ea
- **3-4 smaller outer diameter washers (still need at least 5/8″ inner diameter)** if you do the Home Depot or Rubbermaid cooler – this is because there is an indentation in the plastic on the outside where the picnic tap comes out, so you need some to fit this smaller area in order to get a good seal.
For all of the Watts parts above, the packages can be seen in a picture below.
UPDATE: If you want to purchase a stainless steel false bottom rather than use the braid I describe below, you need one that is 10-12 inches in diameter (measure your cooler first, the one from Home Depot can fit the 12 inch). One of the best deals I’ve found is from Kegworks.com ($31 compared to $40 elsewhere). I have actually switched to this myself, and I absolutely love it. My Igloo fits the 10 inch. It’s a great filter, and it also doesn’t get displaced when stirring or get damaged over time. In this case, you still need to purchase everything below except the cable ties, but only the following parts from above: Watts A-294 (get two instead of one), A-786, A-760, the ball valve, and fender washers). If you do the math, you save about $17 in misc. brass parts, and replace that with a $31 stainless false bottom and a bit of 3/8″ ID clear hose. Only a $13 difference makes this a lot more reasonable than I thought when I first was looking around! If you decide to continue with the stainless braid from the supply line, that’s fine too. The rest of the parts are below for either method.
ACE Hardware (or other small hardware store where you can find these as single pieces rather than buying a pack at Home Depot and thus overpaying)
- Plastic 8″ cable ties (20 count) only need 4 – $2.79
- 5/8″ black rubber grommet – $0.90 – Even if your cooler has a grommet already, you may need this in addition if the grommet doesn’t seal both sides of the hole where your tap is passing through.
- 5/8″ Inner Diameter (ID) Stainless Steel washer (see above photo)- $1 – this can be very tough to find (as others online agree) – It is important to have this one in Stainless because it is going to be in contact with your mash and you don’t want metal ions from nickel plated, adonized, or whatever other kinds of washers might have getting released into the wort (needs to be “food safe”). I ended up getting mine at a local auto type parts shop (non-chain) called Herb’s Fastener & Supply. Definitely call a place before you show up looking for this part – it’s tough to find and you can save yourself driving all over by calling. Let me tell you places I called or visited that DID NOT have this part so you can start looking at other places: Home Depot, Lowes, Ace Hardware, True Value, Pep Boys. Usually these stores have SS washers, but only up to a max of 1/2″ ID, and you need 5/8″ ID.
- Teflon tape to wrap threads for a good seal.
- Keg Lube/Petroleum jelly – I put some of this on my grommet so I could slide the brass nipple through easily.
- Hydrogen peroxide & vinegar – many people have this lying around the house. The purpose of this is you make a mix of hydrogen peroxide & vinegar 1:2 ratio and soak all the brass parts in (that’s what’s happening in the picture) in order to remove trace amounts of lead and such. This is described by John Palmer in his appendices section. It isn’t completely necessary and you’re probably not going to get lead toxicity if you don’t do it, but I did it, and it only needs to be done once.
Now you have all the parts you need (I got all mine above for about $83 thanks to saving on the 10 gallon cooler), here is my next post on how to assemble your mash tun.
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