Author: Marshall Schott

Note: I recently began using a method I’m referring to as “mash in a bag” that essentially replaces the stainless braided hose discussed below with a high quality fabric filter. I understand some will find the more traditional MLT build more appealing so I’ll leave it as is. For those curious about this new process, check out my review of The Brew Bag MLT fabric filter for more details.

Of the many all-grain brewing methods, the one I use most often is batch sparge using a converted cooler as a mash/lauter tun (MLT). While I appreciate BIAB for it’s simplicity, I prefer batch sparge for 2 main reasons: the insulation of the MLT means I don’t have to worry much about monitoring mash temperature and I can brew larger batches. As with most things in this hobby, there are myriad ways to convert a cooler to a MLT, all of which I’m sure work fine. Here, I will share the version I use and prefer, as well as give a couple suggestions for folks looking to save a bit of dough.

I actually have 2 MLTs so that I can make 2 different batches at the same time.

PARTS LIST

THE BUILD

Step 1: Remove stainless braid from inner hose… this is easily the most difficult part of the build because it involves actual work. The way that has worked best for me involved cutting both ends of the hose off using a Dremel, though I’ve also successfully completed this with a hacksaw. Once the ends are off, use needle-nose pliers to grab the rubber hose and gently remove the stainless braid starting from the part closest to the pliers– be careful with this, if you pull too hard or from the bottom, you could deform the stainless hose. Clean up the shards of steel braid on each end of the hose using wire cutters and discard the rubber tube.

Step 2: Remove the spigot from the cooler and be sure to leave the rubber grommet in the spigot hole.

Step 3: Wrap all male threads with 3-5 layers of teflon tape, this will help ensure no leaks later on.

Now that everything is prepped, it’s time to put it all together! After building 5+ of these things, I’ve come up with an order that I believe makes the things easiest.

Step 4: Tightly secure MPT barb to the OUT end of the ball valve. I know, my pics show that I have a camlock on one of my MLTs, which is a remnant of my pumping past, the barb is cheaper and drips less.

Step 5: Tightly secure one end of the pipe nipple to the other end of the ball valve, slide 2 washers and an o-ring onto the nipple (in that order), insert the nipple through outer hole of the cooler, making sure to keep the rubber grommet in place, then slide another o-ring and 1 washer onto the nipple from inside the cooler.

Step 6: Secure the FPT barb to the exposed end of the pipe nipple from the inside of the cooler; tighten to the point that the valve doesn’t wiggle when you open/close the lever, just be careful not to crack the cooler.

Step 7: Place 2 hose clamps onto the braided hose, insert the threaded end of the plug into one end of the hose and secure with a hose clamp, then place the open end of the braided hose on the barb and attach with the second hose clamp.

Here’s the exact order everything should be in from the outside in:

MPT barb -> valve -> nipple -> 2 washers -> o-ring -> COOLER ->

grommet -> o-ring -> 1 washer -> FPT -> SS braid -> plug

That’s it, you’ve just constructed the same mash tun I use. Pretty simple, but it does require quite a few parts. One option that might save you $15-20 is using brass components. Probably the simplest and most cost effective approach involves squeezing 2-3′ of 5/8″ vinyl tubing through the hole in the cooler wall, attaching a plastic valve to the outer tube with a hose clamp, then attaching the stainless braid to the tube on the inside of the cooler. The pressure created from squeezing the 5/8″ tubing through the 1/2″ hole is enough to plug leaks, then all you have to do at the end of your mash is open the valve to collect your wort. To plug the open end of the braided hose, people have had success folding the end over itself multiple times. So the order would look like this:

Vinyl tube -> COOLER -> grommet -> braided hose

Whichever way you go, the final result will be beer. Amen.

Please leave any questions in the comments section below and I’ll address them as soon as I can. Cheers!

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