Converted Cooler Mash Lauter Tun

It's long past time to start making beer again at the Magic Smoke Brewhouse and Grill. The best place to start is at the heart of the brewery: the mash lauter tun, or MLT.

What's this for?

"Tun" is an old word for a barrel, and "mashing" is the process of converting malt into sugary wort, with the idea of fermenting it to make beer. Malt is mixed with hot water and must be kept at exactly the right temperature for an hour or so. For this purpose an insulated container is ideal. Once the cooking is done, the sweet liquid is rinsed from the grains. This "lautering" is accomplished by draining the wort through a strainer and out of the bottom of the vessel. The long twisty straining pipe used in this mash tun is called a manifold.

Cooler

The Coleman Xtreme 70 quart comes cheap and is easily large enough to handle 10 US gallon (40 litre) brews. This cooler has a number of advantages, apart from size: it is well insulated (even the lid), and has a drain port below floor level so that it is easy to get all the wort out.

Bulkhead

Here's how to upgrade the drain with a valve and connection to the manifold. A lot of good construction ideas were borrowed from this bulkhead. Unscrew the plastic drain, saving the plastic washer. Draw around the ¾" PVC coupler, then drill away the outside wall of the cooler so that the coupler can fit inside. (Using a step drill is not recommended because it may removed some of the inner wall that the coupler rests against.) Cut the coupler to size and push it inside the cooler wall. The PVC fitting provides rigidity and prevents the insulation inside the cooler wall from collapsing when the bulkhead is tightened. It does no harm to glue the PVC fitting in place using silicone sealant. The sealant should be clear and without added fungicides: anything labelled for use in an aquarium is suitable.

Now assemble the bulkhead. Wrap PTFE tape around the threads of the ½" close nipple. PTFE tape helps provide a watertight seal and prevents the threads from galling. Take the plastic washer, saved from the dismantled drain, and push it over the threads of the nipple. The ridged side of the washer should face inward where it will fit inside the PVC coupling. Put a 7/8" ID stainless steel shim against the flat side of the plastic washer and screw on a ½" copper x female threaded adapter. This assembly is shown in the picture below left (next to a stainless tee which I ended up not using) and will attach to the manifold inside the cooler. Push the nipple thread first through the PVC tube and out of the cooler. Place another stainless washer around it (galvanized is also OK on the outside of the cooler), then screw on a ½" NPT ball valve. The picture below left shows a male camlock fitting on the valve outlet. It is important not to over-tighten the fittings or the cooler walls may buckle. 

Manifold

The shape of the cooler suits a manifold of this design. Wipe the copper tube with isopropyl alcohol or acetone to remove ink markings. Cut 4x 22½" lengths of ½" copper tube (remembering to file and ream the ends). Next cut slots in these tubes, through which the wort will drain. The slots should be as thin as possible, spaced between ¼" and ½" apart, and should go about one third of the way through the pipe. An easy way to lay out the slots is to lay painter's tape along the length of each pipe and mark the slot intervals on the tape. A hacksaw or dremel is best for cutting the slots. Angle grinder cut-off disks generally make slots that are too wide.

Arrange the tubes so that the centres are 2" apart. Put copper 90° elbows on the one end of each tube, and both ends of the tubs on the outside. Put ½" copper tees on the other end of the two middle tubes. Then connect the ends of the tubes together using 1½" stubs cut from ½" copper pipe. Next make a sort of trombone slide. Take the 2 slip tees and cut their middle arms short. (You also can use regular tees, but you will need to file or drill out the inside stops.) Take the last copper tee and cut its outer arms short, then connect them to the short middle arms of the filed-through tees using ½" long tube stubs. Slide this assembly onto the middle two of the four slotted tubes (see the picture below right).

All that remains is to connect the manifold to the drain using a short length of copper tube. Wiggle the slide to centre the manifold inside the cooler. Mark the positions of the slide tees and drill ½" drain holes in the side arms. The slots should face down against the bottom of the cooler: the manifold in the pictures above is shown upside down to demonstrate ½" slot spacing. At this point, you can solder the elbows and tees to their respective stubs so that there are not so many pieces to look after. But don't solder the slotted tubes to anything, or the slide: these pieces need to be separable so that the manifold can be disassembled for cleaning.

Now put the cooler in the bathtub and add some water to test the bulkhead for leaks. Everything hunky dory? Congratulations, you have made a mash lauter tun. Wash everything thoroughly, using hot water mixed with white vinegar to clean flux off soldered parts, then disinfect using a no-rinse sanitizer. You are now ready to add malt and hot water. Wasn't that Easy? Maybe you're ready to try building a counterflow chiller!

Materials

Cooler

• Coleman Xtreme 70 quart

Bulkhead

• 2x Stainless steel flat shim, 7/8” ID
• ¾” PVC coupler
• ½" NPT stainless steel close nipple
• ½" NPT stainless steel ball valve, full port
• PTFE tape
• Camlock ½" male thread x ½" male adapter, stainless steel (optional)
• Silicone sealant (optional)

Manifold 

• ½" M copper tube, 10'
• 6x ½" copper 90 elbow
• 3x ½" copper tee
• 2x ½" copper slip tee
• ½" copper x female threaded adapter
• Propane torch, plumber's flux, flux brushes, and lead free solder (optional)