DIY Mash Tun
Beer Cooler Conversion

Homemade mash tun...
    for homebrew fun :)
  48 qt beer cooler with drain spigot $23
  Short stainless steel braided faucet connection hose $3.50
  Plastic ball valve $3
  Hose clamps $1
  3/8" OD tubing $1

Total =


I decided to move on up to a larger cooler so I could have no limitations on my future brewing aspirations.  I like this set-up a lot.  It holds heat superbly and has a split lid (w/ beer cup holders on top, I might add) that is great for adding water to raise temp or for mixing the mash with minimal heat loss.  Plus, it was really easy to modify and gets my recommendation for anyone who wants to start mashing their own grains, which should be the goal of any home brewer. This is perfect for batch sparging and gets 75% effeciency with OG 1.054-1.064 (greater eff. the lower the OG, 78%, less eff. the greater the OG, 73%).

Only downside is the slow runoffs, because of the small diameter hosing; easily takes 15 minutes to fully drain while batch sparging. But I have never had a stuck runoff!

Here is how it is set-up...(click to enlarge)


1) You start by removing the stainless steel braiding from the water hose. I did this by hacksawing off one end and pulling the plastic inner-tube out with pliers. This takes a little while. Then just fold over one end of the stainless steel braid and clamp it. The other end is placed over the outlet tube and clamped (loosely, just enough to hold the tube on the braid) into place.

2) The outlet vinyl tube is fed through the drain spigot in the cooler. I cut a slit in the tubing to make it easier to slide through the drain spigot. On the outside of the cooler the plastic valve is connected, which I picked up at the homebrew store. Don't mind the duck tape, its only cosmetic!

3) Finally, tubing is attached with another clamp to the outlet end of the valve and fed to the bottom of the brew pot to collect the sweet wort. The digital thermometer probe is placed in the center of the mash after mixing the grist and water to confirm the mash is at the right temperature (mixing the mash thoroughly, but gently, is ever-important to making sure there are no hot or cold spots). The cord from the probe fits underneath the lip of the lid without any noticeable heat loss.


My previous mash tun
   used for partial mash
  5 gal sports drink cooler $18  
  Threaded brass ball valve (3/4" to 1") $5
  3/4" Brass nut $3
  Brass adapter (threaded valve to 3/8" ID tubing) $3
  O-rings $2
  3/8" ID vinyl tubing <$1
  Total =  $32

This was my original set-up for partial mashes, a 5 gal water cooler. I changed to the above mash-tun for a couple of reasons. The main reason was the additional grain space with the larger cooler. Another, maybe contraversial, reason was the use of a brass valve in this mash-tun. Brass, an alloy, contains lead to increase its machinability. Although the lead is in low concentrations, the heat and acidity of the wort during mashing greatly increases the solubility of the lead, allowing it go into the wort solution. Over time (the many years of home brew consumption) lead accumulation in the body is not such a good thing, so I choose to not use brass fixtures in my set-up (although the debate about plastic accumulation in the body may be valid too, I choose to stay away from heavy metals).

Regardless, this set-up could still be used to create all of the 5 gal batches I have brewed so far (as of the Bonnaroo Bohemian), and I recommend either one of these mash-tun set-ups. There are also 10 gal water coolers which I think would be great for mashing, especially for larger batches or higher gravity beers, but they are harder to find and at least twice as expensive.

Here is the set-up...



1) Unscrew the spigot that comes with the water cooler and affix the brass ball valve with the brass nut, reusing the rubber washers that came with the cooler.



Back to List - Homebrew Adventures