This post will describe how to make a mash tun out of an Igloo Cube cooler (could easily be modified for other coolers) for under $45. I purchased my cooler from Academy Sports & Outdoors for about $15. I think you can get the same cooler from Sams club, just check around. (When purchasing a cooler, make sure it has a standard 1/2" drain valve and enough volume to do the mash) The rest of my parts & (see image above) I purchased at Home Depot. Approximate total cost of the additional supplies was about $27. Unfortunately, you do have to purchase 10 feet of 1/2 PVC pipe (though you only need a few inches of it), but at least it's pretty cheap.
To start, remove the drain valve that came with the cooler:
Now, you want to assemble part of the valve to be inserted into the vacant valve hole. Insert the 3/8" barb into one end of the valve, and the brass nipple into the other end of the valve as shown below. Do not over tighten.
Now you will use the plastic and rubber washer from the original cooler valve, and the 1/2" Female APP (plastic 1/2" nut) to install the new valve on the cooler. Put the valve through the hole from the outside of the cooler, then put rubber/plastic washer, then the 1/2" female nut. Tighten the nut enough to create a seal so that the valve will not leak. The picture below on the left is the valve all put together off the cooler, the picture below on the right is the view from inside the cooler after the valve has been installed.
You have now installed the valve for your mash tun. The next step is to assemble and install the grain filter so you can remove the liquid from the cooler but keep the grain in!
To do that, take the 1/2" PVC pipe and cut 3 pieces, 1 piece 3/4" long and 2 pieces 1 3/4" long. Use a grinding stone or a piece of sandpaper to round the edges of one end of each of the long pieces to make getting the stainless steel braid easier to get on. As laid out in the parts list above, you will insert the 3 pieces of pipe into the 1/2" plastic T. Insert the 2 longer pieces opposite each other, and the smaller piece in the perpendicular part of the T as shown below. Note: DO NOT use any adhesive during assembly. This will allow you to easily disassemble later if required for easy cleaning.
Now, take the stainless steel braided hose and cut off each end (I used a pair of dikes) leaving only stainless braid, and the hose inside. Very carefully (to keep from getting cut by the stainless) remove the hose from inside the stainless braid. Now, take each end of the stainless braid and roll the jagged pieces inward to get rid of sharp edges. You are now ready to take the stainless braid and attach it to the plastic T. One end at a time, work the stainless over the 1/2" PVC pipe. Once you get it attached, you can shape the stainless braid as you wish to fit the bottom of your cooler.
Now, take your assembled T with stainless braid and attach to the end of the female nut on the inside of the cooler. Reminder, don't use any adhesive.
You now have a new Mash Tun! The nice thing about using the stainless braid is that it can be used for any shape cooler, even the round water coolers! If you wish, you can take some of the hose you removed from the inside of the stainless braid and create a down spout to control the wort when emptying the tun. The piece I cut fits nicely into the small compartment in the cooler lid when not in use. Here are some additional pictures of my tun!
I designed this mash tun to be easy to put together and not require any special skills or tools. It comes completely apart for easy cleaning and so far has done me well. When mashing small amounts of grain, you may want to 'pre warm' the cooler with hot water before putting in the grains and water for the mash to help maintain temp.
I hope this post helps in your transition into all grain brewing. Be sure to leave me a comment to ask any questions or let me know what you think of my mash tun plans (good or bad)! Special thanks to Robert Gulley for all of his help in figuring out how to get this built!