How To: Install a Thermometer on Your Mash Tun

Over my last few batches I've been struggling getting consistent original gravity (OG) results.  I'm going to discuss my struggles and changes I've made in a bit more length in a future post, but one of the issues I considered was that I wasn't properly maintaining my mash temperature.  Controlling temperature (both during the mash and fermentation) is one of the challenges of home brewing.  Placing your strike water and grains in a cooler for an hour isn't an exact science and most home brewers don't have access to the same sophisticated equipment that a commercial brewery would use.

The simplest way to monitor your mash temperature would be to just drop your floating thermometer in your mash and check the temperature every so often.  The disadvantage of that process is losing heat each time you open your cooler.  I decided that I want to be able to monitor my mash temperature more closely to have a better idea of the temperatures during the mash.

Here's the process I used to install a thermometer on the outside of my mash tun (credits to John A who posted this procedure on a MoreBeer review of the stainless weld less thermometer kit).  The only challenge of this procedure is to not damage the interior cooler liner when you drill the larger hole for the thermometer bulkhead.  The procedure is very simple and could be done in less than 20 minutes as long as you don't have any leaks.

What you'll need:

Cooler mash tun
Stainless weld less thermometer (I used the 6 in variety, but the 2 in would probably work ok)
Drill
1" spade drill bit
1 1/2" spade drill bit

1.  Decide where to drill your hole for the thermometer.  Obviously this needs to be within the mash so you definitely want it below the 5 gallon mark on your cooler.  Also, don't place the hole too low to avoid trouble removing your false bottom.  I placed my hole about 4 3/4" above the ball valve at the bottom of my cooler.

2.  Drill a 1" hole with your spade bit.

3.  Drill a 1 1/2" hole with your spade bit.  This is part where you need to be careful.  The threads on the bulkhead are designed to fit through a 1" hole, but the depth of the threads is too short to fit through the entire wall of the cooler.  The 1 1/2" hole should go through the exterior liner and insulation only.  Do not damage the interior liner.

You can see from the photo that I mangled the exterior liner a bit.  If I were doing this again I would probably drill the larger hole first.

4.  Insert the thermometer and bulkhead through the new hole.  Sandwich the interior liner between the red rubber washer (this should go outside the liner) and stainless steel washer (inside the cooler).

5.  Tighten all your fittings, test for leaks and you're ready to get your mash on!