If you’re serious about homebrewing you’re going to need a mash tun.
What is a mash tun?
Well, during the fermentation process, you need a way to convert the starches in your crushed – or ‘mashed’ – grain into sugars.
The mash tun is a vessel built to facilitate this process. It should be insulated in order to maintain temperature consistency; which is why we’ll be using a cooler for our DIY mash tun in this tutorial.
Now that we have a better idea what a it does, let’s look at the materials and equipment we’ll need to build a homemade mash tun.
…With just a few parts and tools (and no more mechanical know-how than a 6-year-old), you can easily convert a plastic beverage cooler into a mash tun for less than half that price. –&
Equipment and Tools Needed
- 5-gallon barrel style beverage cooler (feel free to use a 10 gallon if you need to)
- 1/2 inch ball valve
- Corresponding 1 1/2 inch long pipe nipple
- 1/2 Coupling
- Hose barb
- 1 F-style camlock fitting and 1 B-style camlock fitting
- 90° elbow with male and female ends
- 3/4 inch silicone gasket
- 3/4 inch steel washer
- Threaded lock nut
- Standard hose clamp
- Several feet of 1/2 inch silicone tubing
- Stainless steel water heater hose (not plastic!) to be used as a filter
- Roll of Teflon tape
Note that all the hardware should be food safe stainless steel for sanitation purposes. As far as tools go you’ll need:
- 8 mm socket wrench
- Standard pliers
- 2 adjustable wrenches
The 10 Steps to Building a Mash Tun
Now that we have all our equipment and tools assembled let’s dive into the process of how to make a mash tun from a standard cooler. Before we begin, remove the cooler lid. 
If the cooler has an attachment to hold paper drinking cups, remove it too. Also, remove the spout and set it aside. The cooler is now ready to be converted.
- Step 1: Grab the pipe nipple and the Teflon tape. Wrap one end of the pipe nipple with a couple of turns of the Teflon tape. Enough to cover the threads but not so much it will render the threads useless. Then take the silicone gasket and push it up over the pipe nipple until it’s at the midpoint of the nipple, separating the taped half from the exposed half.
- Step 2: Take the large steel washer and slide it up in back of the silicone gasket on the exposed half of the pipe nipple. Then thread the lock nut up behind the washer and lock it into place. At this point, the taped over portion of the pipe nipple should have nothing covering it.
- Step 3: Push the taped half of the pipe nipple through the spout hole on the cooler. Then take the ball valve and thread it over the taped end of the pipe nipple. The Teflon tape, in this case, will help create a watertight seal. Screw the ball valve on until it’s in place but not too tight.
- Step 4: Take both adjustable wrenches in hand. Place one over the lock nut on the pipe nipple inside the cooler and place the other over the end of the ball valve on the outside of the cooler. Turn them in opposite directions until the ball valve is firmly in place.
At this point you’ll need to fill the DIY mash tun cooler part way with water and check carefully for any sign of leakage around the newly installed ball valve.
If you detect any leaks, tighten the ball valve a bit more and test again. If leaks persist, you’ll need to disassemble what you’ve done and start the process over.
- Step 5: Now you’ll use the hacksaw and cut off the connectors at each end of the stainless steel water heater hose. Once you’ve done that pull the tubing out from inside leaving only the stainless steel mesh covering. Use your pliers to crimp one of the ends of the stainless steel mesh tube closed. Then go to the other end and clean up the rough edges by bending them over and out of the way. Don’t leave any frayed edges hanging loose.
- Step 6: Attach the hose barb to the coupling and then screw the coupling onto the still exposed end of the pipe nipple inside the cooler.
- Step 7: Now take the hose clamp and slide it over the open end of the water heater mesh tube that will become your filter. Slide the open end of the mesh tube over the hose barb inside the cooler. Then position the hose clamp over the hose barb and tighten it down with the socket wrench. Your filter is now in place.
- Step 8: Wrap Teflon tape around the threaded portion of each camlock fitting. As with the pipe nipple not so much that it will prevent the threads from being useful.
- Step 9: Work the silicone tubing over the male end of the 90° elbow. This will likely be tricky and take some time but be patient. Make sure you end up with the tubing completely covering the threads.
- Step 10: Take the F-style camlock fitting and thread it into the ball valve. Then take the B-style camlock fitting and screw it into the female end of the elbow. Pop the B-style camlock onto the end of the ball valve setup and your DIY mash tun is good to go.
Final Thoughts on Building a DIY Mash Tun
Building a mash tun is not as difficult as it sounds.
When it comes to how to make a mashing tun the most important things are the size – a 5-gallon cooler may be enough for you or you may need a 10-gallon cooler – and that all the parts are stainless steel for the sake of sanitation.
We get it. Even though we showed you the steps on how to build a mash tun, we’re all busy people and don’t have time to make a homemade mash tun from scratch.
Luckily for you, we have a review guide on the best homebrew mash tuns (January updated) out on the market today.