DIY Mash Tun

This will be a pretty short post compared to the immersion chiller, as there is already so much out there on making mash tuns from coolers.  However, I’ve never been particularly happy with the usual explanations of building a mash tun.  They are always too complicated, use bizarre parts, or use seals that are prone to leaking with the quick changes in temperature experienced when the strike water is dumped in.  I’ve designed this to work with a braid (like from a water heater hose), but I suspect it could easily be modified to work with notched tubes, etc.

This one is easy: put the threaded steel conduit through the hole in the cooler, with just enough on the inside to get a thin nut on with about 1/8″ (3 mm) spare or so.  Put a thin nut on both sides of the cooler wall to keep it in place, like a bulkhead fitting, making it hand-tight.  Screw on a female-female connector on the outside, and a spigot of whatever sort you would like.  Take care to find one that works with the threading on the connector- I had two bottling bucket spigots and only one fit the threads, even through both were the proper diameter.  You could probably also find a spigot to screw directly to the steel conduit, but I had a spare bottling spigot and connector on hand.  Finally, throw on some disposable gloves and knead some drinking-water safe epoxy (or mash it up in a sandwich baggy- just keep it off your skin).  Spread the epoxy around the inner lock nut and about a half inch all around the conduit, forming a tight seal.  You can also put some around the nut on the outside if you like, but this is probably unnecessary.  Let the epoxy cure, aaaand… done.

Inside of my mash lauter tun, including the braid

You can see below where I got some epoxy on the connector from handling it in my gloves, and how the grain actually stained the epoxy a bit darker after a few uses (it started a dull white).  The thin nut for use with the conduit is shown on the upper left.

Stainless steel nut, inner epoxy, mash lauter tun spigot

Mash lauter tun braid

If you plan to use a braided hose, you’ll want a 1″ diameter braided water heater hose; choose a length appropriate for your tun.  Cut off both ends with a hack saw and remove the outer metal braid from the inner plastic tube.  Insert a short bit of thermoplastic or silicone hose into one end to keep it open (these plastics will stand up to the heat), and a short length of copper tubing (or more plastic hose) in the other.  Fold the braid around the copper tube like a coin roll wrapper to seal the end.  Alternately you can just fold and clamp this end, but this might let the entire hose flatten.  Then you can simply insert the open end into the inside of the steel conduit, and it should fit plenty snug enough to keep the grain from reaching the spigot.

This project was pretty cheap, and I had the vast majority of it on hand.  All in all, I suspect it was less than $20 at Home Depot, not including the cost of the cooler.

Complete Parts List:
1: tube drinking water safe epoxy, such as JB WaterWeld (only need about 1 cubic inch)
1: 1″ outside-threaded NPT stainless nipple, male, 1.5″ long steel conduit, (electrical section in store)*
2: thin steel locking nuts (near the steel conduit)
1: 1″ female-female connector, PVC or ABS (plumbing section)
1: 1″ spigot, like for a bottling bucket
1: pair disposable gloves or sandwich bag

Braid:
1: 1″ diameter braided water heater hose, 1 ft long
1: 3/4″ outer diameter thermoplastic or silicone hose, 1″ long
1: 1″ copper tube, 1″ long or another length of hose

* [2014.07.30 UPDATE: Steel conduit in the electrical section is galvanized steel.  The coating will “rust” and form zinc oxide (toxic in high amounts, but unlikely to be harmful in such small quantities) until the coating wears off and the steel rusts.  Both can lead to off-flavors.  I have used the galvanized steel for a number of batches will no issue, but will be replacing it just in case.  I found the stainless part on Amazon from Merit Brass Co.]

– Dennis
Life, Fermented

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