Our new tun features:

• Modified sanke keg.
• Insulated with Armaflex©.
• Bazooka-T© return manifold.
• Adjustable upper manifold.
• Float-control pump switch from Grainger©

The mash tun went into service in August of 2003. Two five-gallon grain bills were run through the system and both batches went rather well.

The mash tun has a float swich that aids in fly sparging. Basically, when water falls below about an inch above the grain bed, the pump is turned on. When the water reaches a high enough level to float the switch, the pump is turned off. Here is a description of the float switch.

Mash Tun Components

I've yet to complete the documentation on the new mash tun; however, I did want to add some pictures of the project as of now.

I opted to go with the Bazooka-T© because it has preformed well in our boil kettle and many people whom I trust have had great results in their mash tuns.

This apparatus is easy to install, easy to clean, hard to plug and considerably less expensive than a quality false bottom.

In this picture you can see the 1" closed-cell foam insulation called Armaflex©. This stuff is awesome. It is easy to cut and glue and, on the first run, held the temperature of the grains at 122° F for thirty minutes without a single degree of loss. It also stays pretty clean and does not absorb water. What water does get pulled into the foam quickly drains and the foam dries very quickly. This is important as wet insulation would be close to worthless.

Note the check-valve in this picture. As the return manifold will be below the level of the water during the sparge, when the pump turns off the liquid will begin to drain from the mash tun back into the HLT. This check-valve prevents the backflow.

I tried using a back flow preventer used on house water systems; however, the pressure needed to crack the seal was too great for my 1/25th HP pump. The check-valve, at a cost of about $1.50, fit the bill.

In our system, water is taken from the bottom of the mash tun, run through a coil in the mini-exchanger to maintain a specific temperature, and returned to the top of the grain bed. This recirculation ensures the water washes over the grains and keeps our temperatures within a few degrees of our target.

We also have a mini-tun, a very small Gott-style cooler used when we do partial mashes. The same ball-valve assembly of our larger tun fits into the mini-tun. We have a smaller manifold that fits the ball-valve assembly. Heat loss in this smaller tun is much more pronounced. We typically loose about 4° F an hour. The copper/brass fittings act as a heat-sink, wicking the heat from the mash into the ball-valve where it radiates to the air. We could put the mini-tun on the same recirulcation loop we do its larger brother; however, when doing partial mashes, the amount of grain is typically so small, we find it more trouble than it's worth to worry about falling mash temperatures.

Construction Details

Our mash tun is made from a ten gallon Gott-style water cooler. We went with the cooler for a few reasons:

• Thermal properties of an insulated vessel.
• Volume of the ten gallon cooler.
• Not as heavy as a sankey keg.

Many people use a rectangular cooler as a mash tun with exceptional results. Still others use a large metal pot. The main advantage of a cooler type mash tun is it's insulation properties -- since the design of the cooler is to reduce heat transfer, hot things stay hot and cold things stay cold. The biggest disadvantage is the temperature of the grain within a plastic cooler cannot be changed by short blasts of heat from a burner.

The conversion of the water cooler to mash tun was pretty simple. First, we needed to replace the thumb valve on the bottom of the cooler with a 1/2" full-port brass ball valve. To save a bit of cash, we used some surplus 3/8" tubing from our mini-exchanger and fabricated a manifold. A 1/2" to 3/8" nip connector connects to the manifold, goes through the original thumb-valve hole and out to the ball valve. The original plastic washer and gasket were used to seal the nip connected on the inside of the cooler. Because the threaded bard of the nip connector is not quite long enough to give us a confident seal on the ball valve, copious amounts of Teflon tape keep the valve from leaking.

This is a good candidate for further refinement as the potential for leaks around the ball valve is high.

More surplus tubing was used to construct the lower manifold. A few 90° elbows and one T-fitting and the basic shape of the manifold took form. This is not, apparently, the best design for a manifold in a circular container. Oh well, works well for us. A Dremel tool helped us cut out hundreds (well, it felt like it) of slots in the bottom of the manifold. These slots allow liquid to enter the tube but keep out the grains. Click on the image for a terrible photo.

As the sweet liquor runs from the lower manifold to the pump to the mini-exchanger, it is returned to the mash tun via the return manifold. This is composed of copper tubing and a few t-fittings and elbows. The idea is to have the sweet liquor gently returned to the top of the grain bed. The return manifold is lowered so it just sits above the grain bed. It's held in place by a pipe clamp on top of the lid.