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Simple HomeBrew Mash Tun – Box Cooler Conversion

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Stepping your brew game up from extract to grain is a smart choice.  Not only will you find it MUCH cheaper to brew a batch of beer, you will also find the beer tasting MUCH better too.  After all,  beer is a product from extracting grain.  Buying a commercial mashing system can prove expensive and is not within the budget of your average home brewer.  What is the solution?  Bust out that old 50 quart cooler and make it into an efficient mash tun cooler!  Total investment $40 if you already have a cooler and $100 if you do not.  Savings?  How about $10-$20 per 5 gallon batch of beer.  You can also do this with a round cooler.  Both work great!

Step 1:
Find a 45-55 quart box cooler that has a drain plug.

Step 2:
Buy a 1/2″ Stainless Steel Valve Weldless Bulkhead For Home Brew Kettle  (any 1/2 valve will do), a 1/2 female / female pipe fitting and a 1/2 male/male extension piece.  Measure the thickness of the cooler wall before buying this piece.  You want it just long enough to create a snug fit from both sides when its all said and done.  A little thread on each side is ideal.  Stainless steel would be ideal but brass works just fine.

Step 3:
Remove the drain plug and its components.  It should be a simple threaded piece.  Save the rings because you will need them.

Step 4:
Install the new ball valve and former fittings.  Your cooler should look like the one below.

Now that you have the exit piece in place you need to put together the inside of your mash tun OR as I call it…the balls of the mash tun.

Step 5:
You have two options for this piece of your mash tun and both are considered efficient.

Option 1
a. buy a stainless steel washer hose and snip both ends of the hose.
b. work the stainless steel coil off of the hard plastic hose on the inside.  Be careful to not cut your hands doing this.
c. on the inside you will need a 1/2 “T” splitter with two 1/2 nipples.  Go stainless if you can afford it.  Brass will work though.
d. coil a copper wire small enough to fit inside of the washer hose and then connect to your T splitter

Option 2
a. go with a 12 inch Bazooka Screen.
b. hook it up to the extension piece that is connected to your ball valve on the other side of the cooler.  MUCH EASIER!
c. buy some rubber weather stripping and line your lid all the way around with it.  This is much better at holding in heat than the plastic on plastic connection.

Option 3:
a. build a false bottom with copper tubing as seen here at Brewer’s Friend.  All designs work just fine.

You are now ready for some ALL GRAIN beer brewing.  Welcome to the world of brewing real beer!  Cheap investment yet a good one!


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  • beermumbo

    Yes, it would be coiling the copper wire and feeding it into the washer hose. It provides stability.

    The other option is a bazooka screen. Same function, Stronger structure, and only a few dollars more.