Easy Upgrade Series: DIY In-line Thermometer for Chillers

Last week, I posted a quick piece on building a DIY counter-flow wort chiller.  You may have noticed that on the end of the chiller where the wort exits after being chilled, there was a little thermometer for measuring the temperature to make sure that the wort was chilled enough to pitch your yeast.

I have a thermometer on my kettle, which was great when using an immersion chiller, but if you’re using a plate chiller or a counterflow chiller, you need to know what the temperature is *after* the wort has gone through the chiller

There are a lot of really complicated ways of doing this, however, I wanted a simple, affordable, DIY method, so I started looking around.  The simplest design that you can buy is called the “Thrumometer.”  The only downside is that it costs $25.  Not terribly expensive, but it seems a bit high for a simple thing like this.  I got to thinking…there has got to be an easier way.


After looking a little further, I discovered a blog post where someone had built a home-made version of this with just a few brass fittings from Lowe’s and an adhesive fish tank thermometer.  Unfortunately, the images on this post are missing.

Since I was going to connect this to the end of my chiller, I decided it would be a little redundant to have a hose barb on each end of the thermometer as this blog post recommends, because then I would need two lengths of hose.  Why not build it so that it fits right onto the end of the chiller?  I could achieve this pretty simply by replacing one of the hose barbs with a brass compression fitting.

compression fitting
source: http://diynetwork.com

This fitting will compress down on the end of the chiller and create a water-tight seal so that I don’t need an extra length of hose between the chiller and the thermometer.

How to Build It

I built this by using a 3″ long 1/2″ brass nipple between a hose barb and a compression fitting.  I attached the three (make sure to use tephlon tape to avoid any leaks!) and then picked up an adhesive thermometer that you find at pet stores, typically used on fish aquarium tanks.  I had to trim up the top and bottom of it slightly so that it would fit, and then just stuck it right to the 3″ nipple.  Because the adhesive is not that strong, and to ensure that it doesn’t come off, I wrapped it with some clear packing tape.

in-line brewing thermometer

And there it is, a simple in-line thermometer that can tell me if my beer is at the right temperature to pitch my yeast, and it connects directly to the end of my counter-flow chiller.  And I didn’t spend $30 on purchasing one!

One thing to note is that the temperature readings are not exact, but when chilling the beer, the goal is just to get it down to an acceptable yeast pitching temperature – you don’t need to be exact.  If you’re looking for something more precise, I would recommend using one of these:
Inline Thermometer with SS Quick Disconnects



Great DIY inline thermometer post but I wonder why not just affix/tape the adhesive thermometer directly onto your tubing? I use silicone which appears to transfer heat well enough for this application.


You could certainly do that as a less expensive alternative. The advantage of doing it this way is having a flat surface for the thermometer to stick to, and having a material that transfers the heat well. Silicone does transfer some heat, but a thermometer on the outside of the silicone tubing will be at least a few degrees off of what your actual wort temp is, but as long as you adjust for that, then you should be ok.


Thanks for the quick reply Chris. It can be an expensive hobby so keep the DIY posts coming!


I’m gonna building it but there is something that I don’t know… do these stickers get burnt with higher temp than the max they display? I usually let boiling wort fill the chiller to sanitize it before letting cold water run.

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