Build a Cooler Mash Tun

The heart and soul of any all-grain homebrewing system is the combination mash/lauter tun. “Mashing” is the hot water steeping process that results in sweet fermentable wort, while “lautering” is the process of separating the wort from the spent grains.) A third critical step in the process is sparging (technically a part of the lautering process), which is the post-mash rinsing of the grain in order to capture as much as fermentable sugar from the barley as possible.

Commercial brewing setups may split the processes of mashing and lautering into their own respective vessels (commercial brewers have a mash mixer or mash tun and a lauter tun, but there is not a third vessel for sparging; the sparge water does
come from a hot water tank, but that is not considered a brewing vessel), but for small-scale homebrewing, combining these functions into one is more efficient in terms of time, money and space.

There are two main functional requirements for a quality mash/lauter tun: the ability to hold the mash at a constant temperature for at least an hour, and a way to drain off the wort while leaving the crushed malted barley behind. The first requirement is very nicely accommodated by a typical insulated beverage cooler. And the wort separation (lautering) can be accomplished with the combination of a gravity-fed ball valve and a straining manifold made from copper pipe
and fittings.

During the initial mashing phase, the grain and hot water mixture (the mash) needs to be held at a constant temperature for approximately one hour. A cooler with thick, well-insulated walls is ideal. Also, choose a cooler with a removable drain valve or spigot. I have had great luck with the Coleman Xtreme line of coolers. For 5-gallon (19-L) batch sizes, a 52-quart (49-L) cooler is a good volume that will allow even fairly high-gravity recipes with some headroom left over for stirring. That is the model used in this project.

Parts and Tools

Hacksaw
Sandpaper
Pliers

For the ball valve:
A “cooler conversion kit” from your local homebrew shop

or

• 1⁄2-inch FPT pipe coupling, approximately 3 or 4 inches long
• 1⁄2-inch pipe nipple, approximately 3 inches long (this may vary based on cooler wall thickness)
• 1⁄2-inch FPT ball valve
• 1⁄2-inch MPT to 3⁄8-inch hose barb adapter
• Silicone (or other food grade material) gaskets to fit
• Pipe tape
• Optional: small rubber sheet for cutting custom gaskets/o-rings

For the manifold:
• Approximately 5 feet (1.5 m) of 1⁄2-inch hard copper pipe (type M or type L)
• (4) 1⁄2-inch 90-degree copper elbow fittings
• (3) 1⁄2-inch “T” copper fittings
• (1) 1⁄2-inch 45-degree copper street elbow fitting
• (1) 1⁄2-inch copper male pipe thread adapter

If you plan to build your project with metric pipe, you will need to choose your fittings appropriately.