DIY Mashtun Thermowell - easy and cheap

[Walker]

I wanted to put a thermowell on my mashtun so that I could check the temp without having to keep opening the lid and losing heat. The thermowells I found online were more expensive than I wanted to pay, so......

Here's what I used:
(1) 1/4" OD copper tubing (about 8 inches of it) - $1.25
(2) 1/4" FIP x 1/8" brass compression coupling - $1.75
(3) 2" long 1/8" MIP brass pipe nipple (shank) - $2.00
(4) 1/8" FIP brass coupling - $2.25 (*see below)
(5) two 3/8" stainless steel washers - $0.75
(6) o-ring - $0.25

Total cost = $8.25

(7) are my probe thermometers - I already had these, so not counting their cost.

* = I really didn't want that freaking coupling. All I wanted was a threaded 1/8" brass pipe cap or a simple nut that would thread onto the shank from the outside, but they didn't have either of those things at Lowe's. I bought the coupling just to get the hell out of the store.

I took a lot of pictures as I did this and am about to post them, so here goes....

 

[Walker]

I started by drilling a 3/8" hole through the wall of my mashtun.

Then I shoved the shank through the hole (it was a TIGHT fit and I almost had to hammer it through). The shank was just barely long enough to fit through the wall of the cooler, and I left a little more threading exposed on the inside compared to the outside.

To seal everything on the inside, I wrapped the threads with teflon tape and pushed an o-ring onto it as far as I could.

On the ouside, I just needed a nut and washer here so that I could get the opposing force necessary to mash my seal on the inside later. A simple nut or a 1/8" pipe cap with a hole drilled in it for the probe would have been great, but I was stuck with a coupling. I put it on just hand-tight at this point.

Addng this port through the tun wall was the hard part.

 

[Walker]

To make the rest of the well, I cranked the compression fitting onto one end of the copper tube until it squealed like a piggy and made a solid connection to the tube.

I measured how far my small digital thermometer probe would stick through the shank and cut the copper tube a couple inches longer than that, just to give myself some room to play with incase my next probe thermometer was longer. I had considered just making it long enough for that really long probe thermometer from the first picture, but that would have needed a well that extended all the way across the diameter of the tun (which would have made getting my false bottom in and out a challenge).

This tubing is soft, so I just crimped the end of it closed with my vice.

 

[Walker]

Now it was time to tighten everything for my seal. I took the compression fitting back apart and threaded the FIP part onto the shank inside the tun, using a stainless steel washer between the connector and the o-ring. The I turned both the coupling on the outside and the fitting on the inside with wrenches to compress everything together and mashed the o-ring.

A little more teflon tape on the male part of the compression coupling, and we're good to go.

And then I threaded on the crimped copper tube to complete the inside work.

The shank had an ID the same size as the OD of my copper tube, so I cut another small piece off and hammered it through the shank/coupling from the outside to make a tighter input port for the probe.

 

[Walker]

And that's it.

I tested it all out with hot water, and there are no leaks anywhere that I can see. The probe in the well reads +/- 0.1*F compared to the same probe placed directly into the water. I can live with +/- 0.1*F.

 

[arturo7]

Nice work, mom!

 

[Walker]

Thanks, sonny.

It only took about an hour total for this (about the same amount of time it took to re-size the images and do the write-up).

I'm adding one to my keggle tomorrow night. :rockin:

 

[Walker]

I tested it all out with hot water, and there are no leaks anywhere that I can see.

Curses! There is a leak. A very very very slow one. Water is getting into the well. I need to disassemble and figure out if it's getting into the foam of the cooler.

Poop!

 

[Walker]

I didn't have the compression screwed onto the shanl tight enough.
Water was able to get into the well, but no water was leaking past the o-ring into the insulation inthe cooler's wall.

Seems solid now!

 

[Hermit]

You might consider soldering the end closed just to be safe.

 

[Walker]

Yeah, I was originally planning to solder the end, but after crimping it shut I am positive it won't leak. (Plus, I was out of gas for my torch. )

 

[The Pol]

Nice solution, sort of like mine....

https://www.homebrewtalk.com/f51/10-thru-wall-therms-pics-too-24946/

 

[Walker]

Nice solution, sort of like mine....

https://www.homebrewtalk.com/f51/10-thru-wall-therms-pics-too-24946/

I had seen yours while searching for others on here who had done somthing similar. Yours is really simple, but I wanted to be able to pull the thermometer in and out with out a leak, so I opted for a closed well.

You mentioned that yours cost $10. How in the world did it cost that much? Does that include the price of the termometer or something?

 

[Walker]

Nevermind.. I see in your thread that the thermometer was $8 and the stoppers under $1.

 

[egurney]

What size is the o-ring?

 

[Walker]

I don't recall what size I bought. I'll have to look at the package when I get home.

 

[Walker]

Following up on this item.... I realized a problem with this thing after using it for a few batches.

The thing is located too high up on my tun. It sits under the water line for a 5 gallon batch but above the grain bed.

The water above the grain is several degrees lower than the actual grain bed, so the thermometer reads a lower value than I am actually mashing at. If I slosh the tun around to get things mixed back up, the temp reading comes back up and is accurate.

Unfortunately, I had to put it where I did in order to be able to get my false bottom in and out, but this resulted in the thing being in an unfortunate spot for my 5 gallons batches.

10 gallon batches have no problem.

Just FYI in case anyone else tried making one of these and was noticing problems with temp readings.

 

[MacBruver]

Do you have any issues when stirring? Seems to stick out kind of far.

 

[Walker]

Yeah, I have to be careful when I stir so that I don't slam into the thing. I end up doing nearly complete circles clockwise, then counter-clockwise, so that I don't hit it hard.

But, any thermowell would create the same issue, so it's not something specific to my particular thermowell.

The probes I am using are fairly short, so I could absolutely cut several inches off this thing and would be able to use it, but I'd still have to be careful when stirring.

 

[chs9]

You mentioned the thermowell is too high - where would you want it? I assume inside the grain bed. Would directly above the false bottom work (~1/2 inch)?

 

[Walker]

yeah, a couple inches above the false bottom would probably be good. I just didn't want to go that low because I would have had to remove the well every time I brewed (to remove false bottom and clean the tun after finishing.)

 

[eanmcnulty]

With a braided hose for lautering the thermowell could really low, couldn't it? Like maybe right above the port. I already have to be careful there anyway when stirring. Nice write up. I am going to make one.

 

[Walker]

Yes, you could put it very low if you have a braid. I think you would probably want to try and hit the middle of your grain bed for the reading, but I am not certain if that really matters or not.

 

[eanmcnulty]

Yes, I think the middle of the grain would be good. I have a 5 gallon MLT and I brew 2.5-3 gallon batches. I need to make it pretty low for 5-6 lbs of grain. When I begin making bigger beers it should be fine in the bottom two-thirds of the grain.

 

[Brewmoor]

You might consider soldering the end closed just to be safe.

I agree. That is how i did mine. Heat it up and drop a bit of solder down into the tube. Then seal the outside a bit too. Grind it down nice and shiny.

 

[Walker]

By all means, solder it if you want. But for those that don't have a torch or are afraid to try soldering(*), just crimp it. It works fine.


(*) Don't be afraid of soldering... it's easy and is a skill that will come in handy more than once.

 

[rooter]

I'm raising this thread from the way back zone...

Big thanks to Walker for the write-up and pics. I crimped the end of my tube and it works just fine, and no leaking into the wall (or through it for that matter). Not only is it very effective, but inexpensive for a CAPP like me.

 

[tnbrewer371]

OP what do you think about making the well a little shorter to avoid knocking it around while stirring, I have the same digital therm as you had in your picture above the yellow one.

 

[Walker]

You can definitely make it a lot shorter if you have the same probe as me, and it would be less of an obstacle for stirring (as well as for getting a false bottom in and out).

I only made mine that long as a "future proof" thing, just in case I ended up with a different, longer probe at some point.

I debated unscrewing my chamber and pulling the copper out, cutting it shorter and then putting it back in several times, but I have since upgraded to a stainless MLT and don't use this one anymore except for when I brew at a friend's house or something.

 

[tnbrewer371]

ok any idea of what the length of well you would recommend knowing how long my digital therm is?

 

[tnbrewer371]

thanks for the quick response, i certainly like this design over the idea of just using a stopper to plug a hole in the wall for the therm??

 

[Walker]

ok any idea of what the length of well you would recommend knowing how long my digital therm is?

Not off the top of my head, but...

Just do the steps listed in message #2 of this thread, and then put your probe through the hole from the outside to see how far it sticks into the tun. Cut your copper as long/short as needed.

 

[bitterpeanut]

Another big thanks going out to Walker!

I just picked up all the parts today and I'm going to do the install tonight. I was hoping to find a cap for the 1/4” tubing instead of crimping the end, but no luck at the local Ace Hardware. The only modification I did to the design was to go with a 1/4” flare fitting and adapted to 1/8” FIP for the inside of the tun. It might have saved me a buck or so, and I already have a flare tool. I did get a 1/8” FIP cap for the outside and I'm planning on drilling it like your original idea. Thankfully the local Ace Hardware had a much bigger selection of fittings than Home Depot.

Thanks for the inspiration.

 

[horseinmay]

You might consider soldering the end closed just to be safe.

That's what I was going to say. There is no way that crimp is going to remain sealed after a few heat/cool cycles. Other than that, I'm putting this on my to-do list. Thanks.

 

[Walker]

That's what I was going to say. There is no way that crimp is going to remain sealed after a few heat/cool cycles. Other than that, I'm putting this on my to-do list. Thanks.

The crimp has remained closed and leak free through dozens of brew sessions.

 

[Cheesefood]

Here's what I used:
(1) 1/4" OD copper tubing (about 8 inches of it) - $1.25
(2) 1/4" FIP x 1/8" brass compression coupling - $1.75
(3) 2" long 1/8" MIP brass pipe nipple (shank) - $2.00
(4) 1/8" FIP brass coupling - $2.25 (*see below)
(5) two 3/8" stainless steel washers - $0.75
(6) o-ring - $
.

Just built one for my keggle and MLT. Cost more than your prices, but still not bad.

Thanks Walker, great DIY for something I've been wanting. Still saved over 50%

 

[bitterpeanut]

Just wanted to post some pictures of my thermowell completed.

I crimped and soldered the end. The thermowell sits around the 2gal mark on the tun.

I used a flare fitting instead of a compression fitting. Just my preference. I have a flare tool sitting around anyway.

I also put a 1/4" cap on the end and drilled a hole.

A worth simple DIY that will make you happy you did.

 

[eanmcnulty]

Nice pics! Been meaning to do that for a year now. Think I might get off my a** and do it. Thanks.

Sent from my Droid using Home Brew Talk

 

[OHIOSTEVE]

gotta put one of these on my HLT... gettin ready to build a 3 tier stand and climbing a ladder to stick a thermometer in the top is not appealing to me.

 

[HibsMax]

I don't know if it's consider bad form to dig up old threads but I wanted to thank the contributors here for helping me with my own thermowell for my plastic fermentation bucket. Now I will be able to tell what temp my beer is at, rather than trying to guesstimate based on ambient temperature and blind luck.