Copper Grain Filter for Igloo Cooler Mash Tun

In my first post, I outlined the process of how to build an Igloo Cube Cooler Mash Tun, using stainless steel braid as a filter media. While the stainless braid works very well, you do have to be careful when stirring the mash not to damage the braid. Because of that, I decided to build a grain filter manifold out of copper tubing and this post explains what I did.

I went to Ace Hardware (Got a gift card from my father in law for Christmas!), and purchased the following items:

4 feet of Straight Copper Tubing (5/8 Ouside Diameter)
4 EPC 90 Degree Elbow (5/8 Inside Diameter)
3 EPC Copper Tee (5/8 Inside Diameter)

I took the straight copper tubing and I cut into the following pieces using a pipe cutter (could also use a hack saw):

2 @ 10 1/4 in
2 @ 4 3/4 in
4 @ 3 1/8 in
1 @ 2 in

The picture to the upper right shows how these pieces were placed to create the manifold.

The single 2 inch piece is going to be used to attach the filter manifold to the output valve. Since the valve is slightly higher than the cooler bottom, you will need to put a slight bend in it. I did this by taking a short piece of 3/8 steel rod and putting it in the bench vise. Then take the copper 2 inch piece of copper tube and place about an inch over the rod sticking out from the vise. Then take a longer piece of 3/8 steel rod and put in the remaining end of the 2 inch piece of copper, applying downward pressure to bend the copper. It's a good idea to go slow and test fit by putting one end of the piece in one of the copper tees and the other into the valve fitting, bending little by little. Once the tee sits on the cooler bottom, you've got the bend you need.

For each of the remaining straight pieces, I then used a small drill bit to drill multiple holes in each piece. It works well if you put a piece of scrap wood underneath so you can drill through straight through, creating 2 holes at once. Try to keep the number of holes uniform across each piece to create a balanced flow. Drill holes evenly until you get the drain flow you want by testing periodically. Any burrs on created on the outside of the copper due to drilling can be removed using a file. You can reference the assembled copper manifold (above left) to see the holes in the copper tubing. I didn't drill any holes in the elbows or tees but that could be done as well. If you plan on using the valve to regulate flow, you can drill many more holes in the manifold than I did.

Right is the finished copper manifold assembled and installed in the cooler mash/lauter tun. I didn't use any solder to sweat the pieces together, but found a good tap from a hammer on all of the ends and elbows creates a pretty tight fit. If needed, it also makes it possible to disassemble in the future for cleaning or storage. If you have questions regarding the installation of the ball valve, please reference the original post which includes detailed mash tun conversion instructions.

Igloo Cube Cooler Mash Tun

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!

To use a copper manifold as a grain filter instead of stainless braid, please reference new post: Copper Grain Filter for Igloo Cube Cooler Mash Tun