River Crew Brewing


Building My 10 Gallon Mash Tun Cooler

The Finished Product - She's A Beauty

The Finished Product – She’s A Beauty

*UPDATE: Rumor has it Home Depot has a new cooler they sell in stores. The spigot is larger, creating a sizable gap. It looks like some people solved this with more washers, but it wasn’t ideal. This link looks to be the same cooler I used: 10 Gallon Rubbermaid Cooler. It’s more expensive than I listed below, and it looks like you can only buy them in-store. Use the store locator to make sure your local Home Depot has this exact cooler. Or, it looks like Homebrew Finds located this cooler at Walmart, which looks to be the same: Rubbermaid 10-Gallon Water Cooler, Orange.

The first step in putting on my big boy pants and upgrading to all grain is getting a mash tun.  A mash tun is used to hold grains at a specific temperature for a long period of time in order to extract those sweet, sweet sugars that give beer it’s flavor and turn into the hooch after the yeast is done with them.  There’s no need for a mash tun with extract brewing since the mashing process is already done for you, and now that I have more space with the new apartment, it was time to get one.

The Start of Something Beautiful

The Start of Something Beautiful

For my mash tun, I chose to build my own out of a 10 gallon cooler.  I’ve been fortunate to collaborate on some all grain recipes with a few very experienced brewers.  They all recommended a 10 gallon tun because it offers enough room for the amount of grain boozier beers and larger-volume batches require.  Props go out to Jonathan Moxey, Chris Lehault, and Andrew Maiorana for the advice.

I was pretty set on buying a pre-made mash tun I saw on Midwest Supply. But then I did some digging around, and I stumbled upon this post over at HomeBrewTalk: Cheap & Easy 10 Gallon Rubbermaid MLT Conversion

$60 vs. $120? Yes, please!

Using that link as my blueprint, I took a free Saturday afternoon and 3 trips to Home Depot to build my mash tun.  Here’s how I did it.  I made a few modifications along the way, and I’ll outline where they were.

Getting Started

Getting Started

First, here’s the inventory with links to what I bought at Home Depot as a reference. Items are listed in order of their use in the project:

The equipment I have outlined above totals $68.30, which is half of what I’ve seen for pre-made tuns.  A sense of accomplishment = priceless.

Here’s how I put this thing together:

First – Remove the Seal
Before the customizing starts, you need to take apart the existing spigot. To do this, hold the spigot outside of the cooler with one hand while unscrewing the piece inside the cooler with your other hand. If you need, use a wrench to loosen the plastic nut inside the cooler. You can disregard the spigot and plastic nut, but hold on to the white rubber seal to use later on.

Second – Create the Braid Filter
This took me the most amount of time for this project. You need to cut the ends off the Watts Stainless Steel Faucet Connector. Now, you might have the tools laying around to cut through metal, but I sure don’t. I picked up a mini hacksaw made to cut through metal) ($6.94), and used a 2-step method to cut it off.

Making the Initial Cut

Making the Initial Cut

To get through the metal braid, I made the initial cut with the hacksaw, and kept going till I got about half way through the tubing inside.  Then, I took out my pocket knife and cut the rest off.  Sturdy regular scissor should do the trick just fine.  I trimmed a few of the stray metal pieces off to avoid them scratching up the inside of the tun.  Careful – they’re freaking sharp.

Switching to Finish Cutting the Braid

Switching to Finish Cutting the Braid

Next, you need to get the metal braid off of the tubing.  This is a bit tricky, and took me awhile to get started.  The braid is kind of like a Chinese finger trap, so pulling it off could cause it rip.  Take a pair of needle nose pliers, open them, and use the 2 sides to push the braid off the tubing. Once you get it going, it’s should push off pretty easy.

Removing the Braid from the Tube

Removing the Braid from the Tube

Take the Watts A-737 Square Plug, put the threaded end into the braid, use a zip tie to lock it into place, and cut off the excess.  The post I followed called for Stainless Steel Hose clamps, but a follow up post showed the screws rusting on the clamps. Rust and beer don’t really mix, so after weighing a couple of options, I went with the zip ties.

It’s almost a filter now, but we’ll save the final assembly for later.

3. Assemble The Internal Bulkhead
Now we’ll start assembling the pieces that connect through the place for the spigot. Take the Watts A-786 Brass Pipe Nipple and apply a few wraps of the Teflon tape to one end of it. Slide on the Stainless Steel Washer from the Create-A-Bolt kit onto the middle of the nipple. it will be a bit loose, but that will change once everything’s fully assembled. Attached the Watts A-298 Female Barb Adapter onto the end of the nipple your wrapped with the Teflon tape.

Completing the Inside

Completing the Inside

4. Insert the Bulkhead
This part is a bit tough, but it’s because we’re making the tun water tight. Place the White Rubber Seal from the original spigot back to its original spot through the inside of the cooler. Take the Nipple with the barb attached and insert the non-Tefloned end into the seal. It might be hard to get it through, but with some negotiating, you should be fine.

5. Assemble The External Bulkhead
Now that the connecting mechanism is in place and the inside is partially assembled, we can get started on the outside. Start by sliding the 5/8″ O-Ring onto the nipple, and apply a few wraps of Teflon tape to the threads of the nipple. Slide the 3 5/8″ Fender Washers onto the nipple as a spacer to make sure everything’s tight once the ball valve is attached.

Starting the Outside

Starting the Outside

Attach the ball valve to the nipple, keeping in mind how the lever for the ball valve opens and closes (I put mine on backwards at first.) As you screw it on, everything should get pretty tight. Apply a few wraps of Teflon tape to the Watts A-294 Male Barb Valve, and screw it into the ball valve.

Attaching The Ball Valve

Attaching The Ball Valve

6. Attach the Braid Filter
Take the Stainless Steel Braid Filter with the attached Square Plug and slide it onto the barb inside the cooler. Use a zip tie to attach it to the barb, and cut off the excess from the zip tie.

Success! With about an hour’s worth of work and the right parts, you build a mash tun and save in the process. Like I said, sense of accomplishment = priceless. But don’t forget to…

The Attached Braid Filter while Testing the System

The Attached Braid Filter while Testing the System

7. Test The System
Everything’s assembled, but does it work? Give your new system a test to make sure. I filled mine up with about 2 gallons of hot water, put on the lid, and let it sit for about 10 minutes. After that, I checked for leaks, and thankfully there were none. I drained the water through the ball valve without any leaks as well.

Testing the System - Success!

Testing the System – Success!

Can’t wait to put this baby to use!

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19 comments on “Building My 10 Gallon Mash Tun Cooler

  1. The plans are great, except in your materials list you specify a Watts A-294 barb adapter which is male, when the A-298 is what is needed and mentioned only later in the instructions. Back to the hardware store.

      • Sorry if it was unclear, Jeff. I tried to spell things out as clearly as I could. Maybe I’ll pull the list into a printable PDF for a shopping list.

        And, believe me, your multiple trips to the hardware store will pay dividends. I love my mash tun, and have been making some really great beers with it.


  2. Just made mine this evening – great directions. Our first mash will be an Irish Red. Thanks for posting this – very easy to follow.

    • One modification I made was to wrap some copper wire around a pencil to make a foot long “spring” and inserted it in the braid filter to help keep the channel open when the grain is added. Picked this up while doing my research on making the Mash Tun.

  3. Anyone else have trouble getting this tight enough? Bought everything exactly like this shows and seems like I’d need to add at least 3-4 more washers to come close to getting it tight.

    • Hey Logan – I had no trouble getting mine tight enough. My ball valve does rotate, meaning it’s not set in place, but I have no trouble with leaks. As long as it’s waterproof, you should be fine.

      • Mine has such a huge gap that water just comes streaming out. I tightened it so tight now I can’t even get it off. I think I might have to cut the brass valve off and try again with a few more washers. Thanks for the tutorial, I greatly have appreciated it.

  4. This is the best site for these instructions. Linking all the items was perfect. I’ve already ordred them from the local Home Depot and will pick them up tonight. All Grain here I come! Thank you so much for this.

  5. brentclarklucy

    Doesn’t work well with this set up on the new Home Depot coolers, the spigot hole is quite a bit bigger. so you have to adjust accordingly. Bigger washers at the very least. I would suggest just upgrading to a larger valve etc. to make it work. Or silicone sealing the washer in which would make it permanent. Leaks using your set up.

  6. brentclarklucy

    Logan it doesn’t work with the new coolers from Home Depot. The spigot hole is a different size.

  7. Has anyone been able to get one together with the new Home Depot coolers? I’m about ready to make the switch to all-grain and want to build my own mash tun.

  8. I’m wondering the same thing about the hole size. I’m about to build one myself. Anyone go with a Home Depot cooler?

  9. Thanks for the tip on the “create a bolt” to get the SS washer! I had previously built the MLT this way and didn’t realize I needed SS and had zinc coated. 6 months later I go to upgrade to a false bottom and I don’t wanna tell you what the washer inside looked like. SS replacement should be good for much longer.

  10. This is great, it not using a false bottom 😉
    The easiest way to separate the braid and tube, is to put it in hot water for 5 minutes, slides right out 🙂 I do suggest using a copper pipe drilled with a couple dozen holes. Slide the braid over it, attach to valve and crimp other end. This way the braid wont collapse from the weight of the grain.

  11. Mountainmatt

    Thanks for the instructions, one trip to the depot and about an hours effort. Total cost $80.
    Built mine using a Home Depot 10 gallon orange cooler. A couple of points:
    1. I Used 2 rubber gaskets and 4 zinc washers on the outside, tightens up very nicely, filled it with 5 gallons of hot water and let it sit overnight, no leaks
    2. For the braid tube, 12″ works, but after cutting the ends it is not close to the other wall. Instead get a 16″ and cut to fit. I wondered if you could find a T connection and make a circular braid tube; some other time maybe.
    3. For cutting the braid loop, just use wire cutters. Cleaner and easier than a hack saw. Also the internal tube is very easy to remove: just push the two ends of the braid at each other, the brais diameter opens up and the tube slide falls out. No pliers needed.

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