In the pursuit of perfect homebrew, failure still makes beer.

The Birth of Big Blue – How to Build a DIY Cooler Mash Tun

Creating something from scratch is always an adventure. I’ve seen as much from my DIY immersion coil, at least. But this is big – I’m going all-grain. The dream has been realized. I feel comfortable enough with my progress as a homebrewer to justify the investment of time, money, and effort into my future beers. I know there will probably be some failures – in the construction of both beers and equipment – but getting to this point is worth a celebration in itself. So huzzah to me!

Now that I’ve sufficiently patted myself on the back, and I’ve already bought my next all-grain barley and hop bills, it’s time to get down to bidness: the bidness of building your own mash-tun. First off, if you’re reading this in hopes to get your own equipment project off the ground, congrats on making the jump. All-grain brewing is definitely the purest and most brewer-controlled method of making homebrewed beers, and you’ve likely run through your share of extract or partial mash brew days. This is a whole new ballgame, ladies and gentlemen. Welcome to the big leagues.


My parts list is as follows. I bought the hardware at Home Depot in Saugus, MA, and the Coleman cooler from Dick’s Sporting Goods in Saugus, MA (on sale, mind you). All together the tun is going to cost me only $55. The cheapest internet price I found for a cooler mash tun was $130. So once again, through elbow grease, you save yourself just over 60% financially while gaining at least 333% more pride in your ability to build stuff. Tim the Toolman, stand aside.

The parts, as listed here.

Parts List for a 9-gallon Coleman Cooler mash-tun:

1x 1/2″ Ball Valve Full-Port Threaded – Brass
1x 3/8″ ID Barb to 1/2″ MIP
1x 1/2″ X Close Brass Pipe Nipple
1x 1/2″ Female APP SXT CPVC (with rubber gasket)
2x 60″ Washing Machine Stainless Steel Braided Hose
Some 1/2″ ID CPVC Pipe (I got a 2′ length)
3x 1/2″ Tee SXSXSX CPVC

I chose a 9 gallon cooler so I could accomodate larger amounts of grain for a 5-gallon batch of beer, i.e. barleywines, quads, and imperials.

The first step was to remove the original drainage port from the Coleman cooler, which was done easily enough with a wrench and some elbow grease. Mine was located at the bottom right side of my cooler. Make sure you keep the rubber washer (gasket/o-ring) that is sandwiched in between the drainage spout – you’ll need it later.

The finished ball-valve assembly

Next, screw the nipple and the barb pieces into opposite ends of the ball valve. You want the barb to go on the end where the valve handle points toward the end; this way, the handle will point away from the mash tun when it’s installed. Hand tighten it only, so you can take it apart easily later to clean it. It’s easier to hand-tighten if you spray the threads with a little WD-40 before you screw them in.

Next, attach the ball-valve assembly to the tun by inserting the nipple side (on the right, above) into the tun, then securing it with the

rubber washer you saved from the original spout, then screwing on the female adapter. Tighten it just enough so there’s a tight seal around the drain hole. Looking at it from the side:
==(ball valve) ||mash tun wall|| {rubber washer}[female adapter]

Female adapter, inside view.

Open, assembled ball valve setup.

Closed, assembled ball valve setup.

After your spout is set up, now you get to the hard part: making your mash screen. This will automatically separate the mash liquor from the mash bed (spent grains), and to do this you have to put in a little work.

Hose-less washer hose, turned steel braid tun drain.

Using a tool of your choice (mine was a hacksaw), remove both hose ends from one of the washer hoses. Carefully, using pliers when necessary, inch the plastic tubing out of the stainless steel braid.  Be careful because the braid is very sharp when it’s frayed. Once the braid is free from the tube, set it aside along with the hose you just removed.

From your 1/2″ piece of CPVC pipe, cut 7 pieces each 1 3/4″ long. These will serve as the couplers between your stainless steel manifold and the tees that construct the manifold arrangement. Work the stainless steel braid ends into two of the coupler pieces. Use a little adhesive (I used Gorilla Glue) to fix the braid ends to the coupler. I found it was best to pull the braid a little bit further through, then glue it in, the snip the remainder off the end of the coupler with a strong pair of scissors.

Fit the hose to the tee on both arms (to complete a circle) and connect the leg of the tee to the female adapter. Do not use any adhesive. It should fit snug enough to stay put, but you will be able to disassemble it for cleaning.

Lay the braid out on the bottom of the inside of the mash tun after connecting it to the female adapter. Measure a circumference that fits comfortably within the confines of the outer braid, and cut that same length from the other hose. Again, remove the end of the new hose and remove the inner tubing to create a double-ended braid. Like before, fit and fix two 1 3/4″ PVC coupler pieces on the ends of the braid with adhesive.

Fit the two remaining tees together in an H fashion using one of your 1 3/4″ PVC couplers. Then, on one tee, attach the new, smaller manifold you just made.

Cut the larger manifold in half at the absolute half point. Use the last two 1 3/4″ couplers to fix the ends of the larger braid you just cut. Attach these ends to the other half of the “H.”

The pieces you should have before connecting them together: two long braids (blue), one short braid (red), a single tee, and an “H” tee setup.

I’ve drawn a diagram below for your reference to the last few steps:

How to measure, cut, and attach your manifold setup to finish our your mash tun.

You now have your awesome manifold, and your fantastic new mash tun. Happy brewing! If you have any trouble following these steps, or if you use this guide, leave a comment and we can chat about it. I can’t wait to use mine… very soon!

Glamour shots:

You can use the hose from the inside of the washing machine hose as a spout nozzle for recirculation or lautering.

I brew, therefore I am. Fo sho.


3 responses

  1. Pingback: DIY Cooler Mash Tun « Brew Log blog

  2. Rick

    I see you went with Gorilla glue to adhere the hose to the PVC, I wonder if that is going to be safe as far as heat and any chemicals leaking out into the hot wort.

    June 30, 2012 at 10:49 am

    • That’s a great point, Rick, and I did a little research to make sure that I was safe to drink the beer that I’m currently brewing on my system. Straight from the Gorilla Glue website, it states: “Gorilla Super Glue can typically be exposed to temperatures ranging from -65ºF to 200ºF without breaking down.” Thank god I’m safe!

      June 30, 2012 at 11:12 am

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