Introduction
A while ago, I was rather taken aback when one of my local homebrew club’s leading lights (OK, it was the Naughty Nurse) showed an interest in my beer brewing techniques – especially in the way I mashed grains. I understand that he has since taken this information and not only built his own mash tun using my approach but has also convinced others of its merit too.
Actually, I cannot claim to have developed this myself. There are several websites describing in brief detail how to do this. I just did the same because I thought that’s what everyone did anyway. For this project, I’ll put my own perspective on this device and provide a much more detailed explanation on how to build this type of mash tun. Instructions on how to use it to best effect are given HERE.
The three main components to construct the mash tun are:
- Beverage cooler
- Spigot assembly
- Stainless steel braiding
The full list of parts is shown below.
Parts List
Choosing a Cooler
I’ve bought both a 5-gallon and a 10-gallon Rubbermaid beverage cooler from a local hardware store. Igloo is another brand that I’ve used in the past. These instructions can be applied to all of these. I typically brew 6-gallon batches of beer. The 5-gallon cooler will mash up to about 12-lbs of grain so this is ideal for most of my beers and costs about $20. The 10-gallon cooler costs about twice this amount and is good for mashes with up to about 24-lbs of grain. I would recommend that you get the 10-gallon cooler if you are making large or strong batches of beer otherwise your mash is going to be very messy. For even larger volumes, a bigger chest cooler with fancy wheels could be used – but make sure that it is fully sealed to take in hot liquids.
Most coolers come with a plastic spigot. On my first (Igloo) cooler, this could be partially opened by inserting a coin under the spigot lever. This was not very elegant, but it was cheap and effective. These Rubbermaid coolers have a push-button spigot which doesn’t work with coins.
It’s very important to control the flow of wort from the mash tun – too fast and it will reduce the effective sparging efficiency and possibly block up the grain bed and, if too slow, it will take forever and start to pull stuff you don’t want from the spent grain husks. So, it’s important to have a spigot that will allow control of this flow and not get blocked. A ½” stainless steel ball valve seemed to be ideal for this purpose.
The parts list above shows stainless steel components which will have a relatively high price (about $30 in total) – I purchased these because I had just been paid and stainless steel is the best choice for food safety, physical strength and resistance to corrosion. Similar assemblies could be put together for cheapskates using brass or even plastic parts. A really cheap and simple method would be to use a simple barbed adapter instead of the ball valve and put a compression (Hoffman) clamp on the flexible tubing that will be attached to this adapter. However, I think a ball valve is much more practical and less likely to leak.
Putting Together the Spigot Assembly
First, remove the plastic spigot that came fitted to the cooler. Check that the 1½” x ½” nipple will fit through the hole left after the original spigot has been removed. Drill out the hole if necessary.
Wrap PTFE tape around the threads on one end of the nipple and thread the nipple into the ball valve inlet to make a good seal as shown.
Slip one of the stainless steel washers over the nipple and push the other end of the nipple through the hole in the cooler as shown. In some instances, a rubber o-ring or rubber washer may have to be placed between the washer and the cooler to prevent leaks.
Slip a second washer onto the end of the nipple and secure the assembly in place with the recessed lock nut as shown. The nut recess should be away from the valve. Firmly tighten the nut with a suitable wrench but don’t over-tighten or you may break the walls of the cooler.
At this point it’s worth checking that the seal is leak tight. Pour some water into the cooler and check that there are no leaks and that the ball valve is able to drain the cooler.
Now fit the FPT barb onto the inside of the nipple as shown. This probably won’t seal well but that’s not important. Just make sure it’s tight enough not to fall off during use. No PTFE tape is needed.
Finally screw the MPT barb into the outlet of the ball valve as shown. PTFE tape should be used to get a good seal or else bubbles of air may form while draining the mash tun and cause possible hot-side oxidation.