My $15 Mash Tun

After a stroke of luck in which I spotted an old cooler on the side of the highway, I finally have the last piece to complete my all-grain home brewing system. Some people order stainless steel ball valves and pieces which aren’t favorable to a budget. With a trip to Lowe’s I was able to convert it into a cheap 52 quart mash tun.

For those that aren’t homebrewers, a mash tun is a piece of equipment used in grain brewing. It’s a vessel used to convert the starches found in crushed grain into fermentable sugars. The mashing process involves steeping the malted grains in hot water which allows enzymes to break down the complex starches into simple sugars. These sugars are what the yeast can then ferment into alcohol.

Up until now I have been brewing exclusively with malt extract. This is basically just condensed, pre-mashed mixture in powder or syrup form. But now I can do my own mashing. My co-worker Derek Springer equated extract brewing vs. all-grain brewing is like the difference between making boxed mac and cheese with the cheese powder vs. cooking it from scratch.

The project started when I was driving down the highway to meet my wife for lunch. I spotted a cooler on the side of the road, and it was still there on my way back home. So I stopped and picked it up.

It’s a little beat up and dirty, but it holds water without any leaks! Now I have the most expensive piece of the build, but it’s free.

The first step was to remove the drain plug so I knew what size tubing I needed to get. It was on there tight, but easy enough to remove with pliers.

Next was a trip to the hardware store. I’ve read a few blog posts with other DIY builds so I had a general idea of what I needed. 20 minutes of standing in the aisle trying different sized tubing and fittings, and I had all the supplies.

• 1/2″ OD x 3/8″ ID vinyl tubing – about 5 to 10 feet
• 3/8″ OD x 1/4″ ID vinyl tubing – 12 to 15 inches
• 1/2″ threaded PVC valve
• (2) 3/8″ hose barb with 1/2″ fitting
• 1/2″ x 12″ stainless steel braided water hose
• (4) 1/2″ stainless steel hose clamps – not pictured
• Teflon tape

The hardest and most time-consuming part of the build was cutting the ends off the braided hose. Due to my lack of power tools (and where the hell did my hacksaw go?!) I was forced to use a utility knife.

Tip for anyone building your own: be careful of these steel braid ends. If they fray they are very sharp. I stabbed my fingers at least 8 times working with it.

Sliding the tubing out of the mesh was another challenge. It kind of reacts like a Chinese finger trap when you pull on it. I found the easiest thing to do was to get it wet and twist as I pulled it out with the pliers. It’s definitely a slow process.

After the tubing was out of the mesh, I realized the 1/2″ OD vinyl tubing would be just a tad too big to slide in easily. Luckily I had some 3/8″ tubing that I was able to use.

Alternatively, you could leave the mesh braid hollow, but I wanted to give it some reinforcement to keep it from potentially crushing under the weight of the grain. Depending on the recipe, it can use upwards of 20 pounds of grain (and more!). Add to that the pressure of a few gallons of water and you can see why I might be concerned.

So I took my 3/8″ tubing and drilled holes on all sides about 1/4″ apart. The idea was to make it porous and allow water to penetrate, but keep it structured enough.

Next was sliding the perforated vinyl hose into the mesh braid and clamp everything together. I used a hose clamp to keep the braid and tubing attached, and another to fasten the 3/8″ hose to the 1/2″ hose.

On the other end of the mesh braid I folded it over on itself and crimped it a few times to close it up.

Then I cut about a 6 or 8 inch length of the 1/2″ hose and put it through the cooler drain hole. It was about 1/16″ too small in diameter, so I wrapped the teflon tape around it to create a water tight seal.

Now that the inside of the build was done, I just needed to attach the ball valve. I wrapped some teflon tape around each of the hose barb threads and threaded them on to the valve.

All that’s left to do for the build now is attaching the input of the valve to the hose, and adding some more hose to the output. I cut about a 5 foot length of the vinyl hose so I could be sure it would reach into my boil kettle.

It’s done! I’ll probably go back and add a couple hose clamps to each end of the ball valve just to make sure it’s secure.

Then the moment of truth came — time to test for leaks!

I took the whole thing outside and filled it about 3/4 full of water. Then it sat for 45 minutes to make sure everything was water tight under pressure.

It worked pretty great. No leaks and it drained beautifully. There was a small drip around the cooler drain hole when I started moving the valve around to open the flow. It should be an easy fix with just adding more teflon tape.

Overall I’m happy with how it turned out. And for $15 total cost it’s hard to beat. Now I can’t wait until my next brew day when I can use it for my first full all-grain batch!