How to build a mash tun cooler

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If you’re an all-grain brewer, undoubtedly, you’ll be using some sort of a mash tun to steep your grains.  You can buy an expensive store-bought one, or you can make one out of an old cooler you might have lying around for far less money.  In my experience, the homemade mash tun cooler can work as well or better than an commercial one.

Mash tun cooler parts list:

  • One old chest cooler with a drain
  • Steel mesh covered toilet supply line (at least 12″)
  • 3 adjustable hose clamps that will clamp down to 1/2″
  • Pack of #10 O-rings
  • Between 4-6 feet of plastic 1/2 ID hose
  • 1/2″ MIP to 1/2″ barb fitting for the inside of the cooler
  • 1/2″female to barb ball valve for just outisde the cooler
  • 2 conduit threaded washers (this holds your pipe nipple in place)
  • 1 1/2 inch brass pipe nipple
    • Optional (to weigh down the filter hose)
    • 1/2″ barb to male threaded connector
    • 1/2″ brass female end cap

Mash tun cooler tools list:

  • Heavy duty scissors, clippers, or nippers that will cut through the wire mesh and inner hose.
  • flathead screwdriver
  • two channel lock pliers

I had the cooler lying around, and bought the remaining supplies for about $45 total.

Mash tun cooler build instructions:

First thing’s first in the mash tun cooler build: cut off the existing connectors on both ends of the supply hose.  You’ll then see a rubber hose inside.  Gently pull with needle nose pliers the hose out of the middle, while pushing the mesh with your fingers.  With a bit of patience, you should be able to get the hose out completely, leaving you with a wire mesh that we’ll use as a pre-filter before the drain.

mash tun filter

Gently pull the rubber hose out of the wire mesh by pulling the hose and pushing down the mesh away from the direction you’re pulling the hose.

Now that you have your wire mesh, let’s close off the end and put a connector on the other end to attach to the drain (brass pipe nipple).  As I stated above, the addition of a barbed connector and an endcap on one end of this wire mesh is totally optional.  I added it because the weight keeps the mesh under the hot wort much easier.  The first time I built this mash tun, I just crimped that end with pliers, and I had a tough time keeping it at the bottom of the cooler.  However, this part is completely up to you.

If you choose to weight down the end, use a connector that is barbed on the mesh side and threaded male on the other side.

If you choose to weight down the end, use a connector that is barbed on the mesh side and threaded male on the other side.


Finished view of the back end of the grain filter.

Slide the hose clamp on first, put the barb in the mesh, and tighten the hose clamp as tight as you can get it.  Then screw on the endcap.  You can use teflon tape here if you like, but with this piece being inside the mash tun, if it leaks, there are no consequences, so I didn’t bother. On the other end, I attached the barbed to female connector in the same manner.


Barbed connector going into the mesh on the drain connection end of the hose


The completed connection after the hose clamp is fastened

The next step is to remove the drain from the cooler.  Mine was a simple unscrewing of the drain nut, and then pulling the plastic nipple out.  Be sure to save any rubber grommets, o-rings, or seals, as you can use them on your metal pieces you’ll use shortly.

Remove the old cooler drain before transforming into a mash tun cooler

Simple removal of the cooler’s plastic drain

Once you have the original cooler drain removed, insert your brass pipe nipple in the hole.  Use the O-rings and/or the original drain seal on the outside and inside, then screw on the washers to keep the pipe nipple in place on your new mash tun cooler.


Pipe nipple inserted with the O-ring attached


Pipe nipple installed with the original rubber seal and a new O-ring

mash tun cooler drain connection

Tighten the conduit threaded washers with a pair of pliers on each side for a water-tight seal

Now that your pipe nipple is in place, and has been tightened and liquid proofed with the O-rings, you can connect the mesh filter pipe on the inside of the mash tun cooler.


Stainless metal mesh filter tube connected to the drain hole

The last two steps in your mash tun cooler construction involve connecting the ball valve to the drain, and connecting the drain tube to the ball valve.

Connect the clear tubing to the barbed end of the ball valve with a hose clamp, and tighten the hose clamp as far as you can.


Ball valve attached to the drain hose with a hose clamp

Finally, attach the ball valve/drain tube to the pipe nipple on the outside of the cooler and you’re done with the mash tun cooler build!

Happy brewing!!!





Category: Beer