Whether you’re counting your pennies or trying to assemble a world-class homebrewing system, you can build a combination mash tun/lauter tun to meet your needs.

This is a look at three types and how to make them. The first two, in common use, are the double plastic bucket and the retrofitted picnic cooler. The third is the ultimate, tricked-out, gonzo 15- to 20-gallon model. This has some interesting features that you may choose to
incorporate into your own dream system at some point.

All mashing vessels have certain things in common: a chamber, preferably insulated, to hold the grain; a false bottom below the chamber with slots or holes just large enough to prevent the crushed grain bits and husks from falling through; a small space underneath the false bottom; and a drain or spigot to run out the wort from under the false bottom. In addition some method of gently sprinkling hot sparge water on top of the grain bed is needed.

Generally, the more insulation around the tun, the better. Coolers come well endowed. But if you do choose to obtain a double bucket setup, you’ll need to arrange some insulation—foam, a blanket, something—or else the heat drop will affect the mash in progress.

Grain depth is important. For the homebrewer eight to 12 inches is probably optimum. You want it deep enough to form a good filter bed to separate wort from the grain and clarify the liquid but not so deep that the flow is difficult. As far as size goes, the volume of the mash you put in the tun will be up to the same volume as the batch you’re brewing, with the exception of really strong beers—over 1.085 specific gravity—which will be somewhat larger.

You can get by with a five-gallon bucket for five-gallon batches, but the mash will often be right up to the top. With coolers it is probably a good idea to have 50 to 100 percent extra capacity (7.5 to 10 gallons) to allow your sparging device to fit under the insulated lid.

Also, it is a good idea to minimize the volume in the area under the false bottom. This avoids some of the hydraulic problems caused by the suction of wort leaving the vessel. Two inches is the absolute max, but commercial breweries use as little as a quarter of an inch.

The Double Bucket
Materials:

• Two identical 5-gallon buckets         
• Spigot with fittings
• Drill with 1/8-inch bit
• Plastic hose      
• Insulation     
• Screen mesh

    
The double bucket mash/lauter tun is the cheapest to put together and works perfectly well. It’s durable and can be used for everything from wheat beers to barley wines. This system is fabricated from two identical five-gallon buckets, the kind they’ll sell you for 50 cents at the burger joints (or more upscale food storage containers from the restaurant supply house) nested together. Most people drill about a thousand 1/8-inch holes through the innermost bucket, allowing it to serve as a screen to separate malt from wort. You might prefer to cut out part of the bottom and replace it with screen wire, as this takes one-tenth as much time.

You will need to attach a spigot as low as possible on the side of the outer bucket. Most homebrew supply shops sell a plastic drum tap designed for this purpose. Ideally, the tap should be fitted with a plastic hose so the wort doesn’t splash into the receiving bucket below, aerating it and creating the potential for oxidation trouble later.

Drill or cut a hole of appropriate size, push the valve through, then tighten the nut down on the rubber washers on the inside to seal. Be sure to tighten well and avoid twisting when hot, as expansion can cause the plastic parts to loosen.

You may find what you need for a spigot at the hardware store, but getting the right fittings to seal tightly through the plastic wall can be a challenge. For valves use ball valves rather than the faucet type, as ball valves open quickly.

To go through the side of the container, you may have luck finding a good bulkhead fitting. The most common bulkhead fittings are flare or compression fittings. These aren’t the ideal options for your needs because they complicate your ability to fit a valve on the end. If you can find a short length (two to three inches) of brass 1/4- to 1/2-inch NPT (standard plumbing) pipe, a good hardware or plumbing supply shop ought to be able to thread the whole length of it. The threaded pipe can serve as your bulkhead fitting.

If you want the cheapest possible vessel, drill a very clean hole (a wood-boring brad point works best) through the side where the valve would go. Insert a length of vinyl tubing that is 1/8-inch larger in diameter than the hole, forming a very tight fit. The hose can be pinched shut with one of those plastic shut-off clips. Perfectly functional, just not too sexy.

For the false bottom the most readily available choice is bronze window screen. Cut it 1/4-inch larger than the size desired, and fold the edges under to hide the loose ends. This can be attached to the cut-out bottom of the inner bucket with eight small (3/16-  by 1/2-inch) stainless steel machine screws, evenly spaced around the edges. If you can find stainless steel screen material, you can be assured of having something absolutely inert. It’s cheap at the scrapyards but brutally expensive ($10-plus per square foot) when purchased new.

Once you’ve got the false bottom and spigot affixed, you’ll need to arrange for some kind of insulation. The simplest is a layer of plastic, such as a garbage bag, topped with a heavy blanket or sleeping bag. Those silver “emergency blankets” work nicely, as they are water resistant.

For something more enduring in the wet environs of the brewery, you should think about making something out of foam insulation. The Styrofoam jackets that come on the 6.5-gallon acid-bottle carboys are a good starting point, if you have one of them. Just take a thin serrated knife or keyhole saw and carve the thing up to work for you.

Cut one deep slot down the side to accommodate the spigot as you drop the mash buckets into the jacket. The edges can be finished with duct tape. If you save the portion removed for the spigot and cut off the lower inch or two, you can pop it in place, maybe secured with self-adhesive Velcro strips, to complete the insulation.

You can also use foil-faced building insulation (polyisocyanurate), to fashion any kind of jacket you want. Cut it with a sharp matte knife, and finish edges and assemble with duct tape.

Picnic Cooler Mash Tun
Materials

• Picnic Cooler
• Spigot with fittings or other draining system

Either:

• Copper water pipe
• Copper tees and elbows
• Hack saw or Dremel tool

Or:

• Screen mesh or perf plate
• Sheet stainless steel or sturdy plastic
• Gasket such as vinyl tubing

Picnic coolers are very popular mash tuns and are also quite easy to make. The use of an insulated container with a spigot already in place saves a lot of effort.

Coolers come in many sizes and shapes; you will want one up to twice the size of the batch you’re brewing. For five-gallon batches, 36 to 48 quarts is good. This size gives you plenty of headroom for a sparge arm under the lid. Don’t go larger than this, or the grain bed will be too shallow for decent filtering action.

Round and rectangular coolers are available. Round ones are somewhat preferable because they keep the mash in a more compact mass, resulting in less heat loss, and you can use a rotating sparge arm. But rectangular ones work fine, too, so it’s up to you.

The most common form of the cooler-mash tun uses a copper manifold instead of the usual false bottom. This arrangement is not unique to homebrewing. Anheuser-Busch uses a similar devise for lautering, called a strainmaster. An advantage of the copper manifold is that it solves hydrolic problems sometimes caused by too much space under a false bottom.

The homebrew version uses a branching network of slotted copper pipe connected to the spigot. Wort flows from the mash into the slits, through the pipes, and out the spigot. Since every cooler is different, you’ll want to customize the design of your manifold to work best in your vessel. The goal is to evenly space the pipes throughout the cooler, about three inches apart.

The common design in a rectangular cooler is a pitchfork-shaped arrangement. In a circular cooler moth antennae may be a better model. It is best to get a big sheet of paper and draw a line to indicate the shape of the inside bottom of the cooler. Locate the spigot, then draw your design. When you start cutting pipe, you can trial-fit the thing together right on the paper.

Use 1/2-inch diameter copper water pipe. This fits neatly into the tees and elbows designed for it, so no solder is required (which is good, since even lead-free solder is bad for beer), and everything comes apart for easy cleaning. If the fittings seem a little loose, they may be tapped gently with a hammer to pinch a little tighter, but don’t overdo it.

A hacksaw makes acceptable slots for wort drainage. Saw halfway through the pipe, placing a cut about every half an inch. If you prefer, use a Dremel tool (die grinder) with an abrasive cutoff wheel, which will make narrower slots.

Every cooler has a different arrangement for the drain valve—which means you need to use a little ingenuity hooking up the manifold inside and a ball valve outside. You may want remove the existing valve or drain-plug assembly entirely, or simply jam a piece of appropriate size copper tubing into or through the opening. Many times, especially in the round coolers, the spigot unbolts, leaving a hole just over 1/2 inch through which pipe may be run and sealed with silicone bathtub caulk. By the way, silicone is the only sealant/adhesive readily available that may be used in contact with beer.

If you prefer, a false-bottom works just as well in a cooler as a manifold. (See the discussion below regarding materials and design.)

As you can see, there are many ways to build a basic mash tun. What you end up with depends on what’s readily available and on your ingenuity in fitting all the pieces together. The next tun is a little more flashy for larger batches, but the add-ons and methods work great for any tun you can think up.

Gonzo Tricked-Out Lauter Tun for 15-20 Gallon Batches
Materials

• Stainless steel beer kegs

Or:

• Food-grade plastic buckets
• Spigot with fittings or other draining system
• Screen mesh or perf plate
• Sheet stainless steel or sturdy plastic
• Gasket such as vinyl tubing

A bigger lauter/mash tun can be built along the same lines as the ones described above by using bigger vessels. Stainless steel beer kegs or food-grade plastic “trash cans” are the vessels of choice, although many other vessels can serve just as well. Working with beer kegs requires specialized tools (translation: “pain in the neck”), and the properties of kegs aren’t really needed in a lauter tun. You’re better off using a food-grade plastic container. A 32-gallon bucket is suitable for making 20 to 25 gallons of beer. With brews larger than that the grain bed becomes too deep, and a larger container is required.

If you outfit a beer keg with a false bottom because you think you’ll put it on the stove to do a step mash, be advised that this doesn’t work very well. Although manufacturers are selling these systems, the screen blocks heat from flowing from the bottom of the pot to the mash on top. The stuff on the bottom can scorch, since there is no way to get in there to stir it up. If you want to do step mashes, you should do them in your brew kettle, then transfer to the lauter tun for runoff and sparging.

The size and weight of the wet grain puts additional demands on the engineering of the large lauter tun. The false bottom must be either pretty sturdy stuff or supported by a number of small legs spaced evenly across it. For a perforated bottom look in junkyards or industrial surplus stores for sheet metal with pre-punched holes called “perf plate.” If you must, you can make this yourself with sheet metal and a drill. If you’re using screen mesh rather than perf for the bottom, it needs to be supported on a piece of sheet stainless steel or sturdy plastic (polypropylene, high-density polyethylene, nylon, polycarbonate) with slots or holes cut out of it.

It is a good idea to put one or two handles on the screen or perf false bottom so that it may be removed from the bottom of the vessel without a fight. Again, make sure the screen is above the level of the valve and its attaching nut. In an ideal world the drain would come off the bottom rather than lowest point on the side, but this complicates things.

If you can figure out a way to do it manageably, this is the best way, as it minimizes the volume under the false bottom. It may be smart to put a gasket around the outside of your false bottom to get a better seal. A length of 1/4- to 3/8-inch vinyl tubing slit along one side works perfectly.

A vacuum gauge is a useful addition to a large lauter tun, because there can be considerable suction if the mash is run off too fast, causing compaction of the mash. With a gauge you can monitor this and cut down the outflow in the early part of runoff, limiting the suction. Later, when the bed is well-established, the tap can usually be opened full bore.

The gauge should be attached to a piece of stiff tubing (plastic, copper, etc.), which goes through the false bottom to the space underneath. One brewer found his gauge at a surplus store; it was originally a pressure gauge from a CPR training dummy. He opened up the case and bent a little wire so the gauge now registers vacuum as well as positive pressure. It’s very sensitive, and the needle moves with the slightest drop in pressure under the false bottom.

Easy Additions
Each of the tuns described above can be improved with a few simple additions.

One good idea is to put a swan neck on the spigot. This brings the outflow up to a level above the false bottom, and using it prevents air from becoming trapped below the screen, creating suction and, thus, outflow problems. This may be a short length of metal tubing that connects to the spigot on one end and the plastic hose on the other. Most times these swan necks can swivel to adjust their height. The same effect can be achieved by just bringing the tubing up to the level of the false bottom before it goes on down to the receiving bucket.

A thermometer probe is another accessory that makes life easier. One with a short stem interferes less with insertion and removal of the false bottom. A dial-type thermometer can be installed with a compression bulkhead fitting. Just find a fitting of the same size as the stem diameter, and drill it through to allow the thermometer to go all the way in. Attach the thermometer using the metal compression ring; a small rubber O-ring makes a more temporary installation.

If you can swing it, another thermometer, inserted into a “tee” fitting just before the sparging arm will display the temperature of the sparge water as it falls on the mash. This will be lower than it is in the hot liquor kettle, and knowing its temperature can be very helpful in maintaining proper sparge temperature.

A 1/4-inch compression tee can be used; a standard laboratory glass thermometer is inserted into one of the sides and sealed with a small rubber O-ring in place of the metal compression ring. Be sure the bulb of the thermometer is just touching the fluid stream. Also, mount the thermometer so it is out of the way and unlikely to get snagged and broken. A dial-type thermometer without the hazards of glass can be used.

Sparge Arms, Sprinklers, etc.
There are many ways to drizzle water on top of your mash bed. The idea is to let the water flow evenly over the top of the bed without disturbing it. A mechanism connects to a container of hot water and is fed by gravity or a pump. It may be built into the lid of the lauter tun or hooked to the sides in some fashion.

The simplest device is 1/4- to 3/8-inch copper tube, bent into a loop that fits the shape of the vessel. Holes or slots on one side allow water to sprinkle out. The smaller the holes, the more spray-like the effect. Drill-holes of 1/32-inch will be about right. Place them about every 1/2-inch.

If you cut slots with a hacksaw, just barely cut through the wall of the tubing. A razor saw, available at hobby or art stores, will make a better, finer cut. Be sure to bend the tube into the appropriate shape before drilling or sawing.

The rotating sparge arms made by Listermann Manufacturing are especially useful. They are simple, durable, and come in a variety of sizes.

Be sure to remember that the first cloudy wort that gets recirculated through the mash has chunks in it that will clog the small holes in your sparge arm. The wort needs to be gently floated on top of the grain bed without disturbing it.

So there you have a number of ways, from simple to complicated, to capture the precious juice of the barleycorn. Whatever variation you choose, your all-grain beer will be delicious.