What to look for in a Cooler
In this section I will describe how to build a mash/lauter tun out of a common picnic cooler. Building one is easy and inexpensive and is the easiest way to start all-grain brewing. You may use either a rectangular chest cooler or a cylindrical beverage cooler. You can use either rigid copper tubing with slip fittings or soft copper tubing with compression fittings. Everything you need to build one of these tuns is readily available at a hardware store.
The shape of the cooler is only important in that it determines the grainbed depth. It is important to have a minimum grainbed depth of at least 4 inches. The optimum depth at this scale is probably about 1 foot. If it is too shallow, it won't clear sufficiently; too deep and it will tend to get stuck. A five gallon round cylindrical Gott cooler works well for 5 gallon batches; it can hold 12 pounds of grain and the water to mash it. Naturally, the 10 gallon size is good for doing 10 gallon batches. These coolers have convenient spigots which can be removed to make it easy to drain the wort.
Figure 161 - Beverage Cooler and Detail of Modified Spigot Hole. A suggested method for securing the manifold outlet through the cooler spigot hole is shown here. Threaded plastic or brass bulkhead fittings can also be used.
The rectangular ice chest coolers may have drains but often do not. These coolers are usually sized at 20, 24, 34 or 48 quarts (5-12 gallons) and offer a good choice for any batch size. My preference for most 5 gallon batches is the 5 gallon cylindrical or the 24 quart rectangular coolers. These sizes give a good grainbed depth for 1.040 - 1.060 beers. If you are using a rectangular cooler that does not have a drainage opening or spigot, lautering works just as well if you come over the side with a vinyl hose - siphoning the wort out. You should use a stopcock or clamp to regulate the flow, and as long as you keep air bubbles out of the line, it will work great.
Figure 162 - A 6 gallon Rectangular Mash/Lauter Tun. The slotted manifold connects to vinyl tubing with a stopcock for controlling the flow.