Author: Marshall Schott
Note: I recently began using a method I’m referring to as “mash in a bag” that essentially replaces the stainless braided hose discussed below with a high quality fabric filter. I understand some will find the more traditional MLT build more appealing so I’ll leave it as is. For those curious about this new process, check out my review of The Brew Bag MLT fabric filter for more details.
Of the many all-grain brewing methods, the one I use most often is batch sparge using a converted cooler as a mash/lauter tun (MLT). While I appreciate BIAB for it’s simplicity, I prefer batch sparge for 2 main reasons: the insulation of the MLT means I don’t have to worry much about monitoring mash temperature and I can brew larger batches. As with most things in this hobby, there are myriad ways to convert a cooler to a MLT, all of which I’m sure work fine. Here, I will share the version I use and prefer, as well as give a couple suggestions for folks looking to save a bit of dough.
I actually have 2 MLTs so that I can make 2 different batches at the same time.
PARTS LIST
- 70 qt Coleman Xtreme Cooler
- 1/2″ Stainless Ball Valve (brass works too)
- 1/2″ Stainless MPT Barb
- 1/2″ Stainless FPT Barb
- 1/2″ x 1 1/2″ Stainless Nipple
- 1/2″ Stainless Braided Hose
- 1/4″ Stainless Plug (brass works fine)
- (3) 3/4″ Stainless Flat Washers
- (2) Small Stainless Hose Clamps
- 3/4″ ID O-Rings (#15)
- Teflon Tape
THE BUILD
Step 1: Remove stainless braid from inner hose… this is easily the most difficult part of the build because it involves actual work. The way that has worked best for me involved cutting both ends of the hose off using a Dremel, though I’ve also successfully completed this with a hacksaw. Once the ends are off, use needle-nose pliers to grab the rubber hose and gently remove the stainless braid starting from the part closest to the pliers– be careful with this, if you pull too hard or from the bottom, you could deform the stainless hose. Clean up the shards of steel braid on each end of the hose using wire cutters and discard the rubber tube.
Step 2: Remove the spigot from the cooler and be sure to leave the rubber grommet in the spigot hole.
Step 3: Wrap all male threads with 3-5 layers of teflon tape, this will help ensure no leaks later on.
Now that everything is prepped, it’s time to put it all together! After building 5+ of these things, I’ve come up with an order that I believe makes the things easiest.
Step 4: Tightly secure MPT barb to the OUT end of the ball valve. I know, my pics show that I have a camlock on one of my MLTs, which is a remnant of my pumping past, the barb is cheaper and drips less.
Step 5: Tightly secure one end of the pipe nipple to the other end of the ball valve, slide 2 washers and an o-ring onto the nipple (in that order), insert the nipple through outer hole of the cooler, making sure to keep the rubber grommet in place, then slide another o-ring and 1 washer onto the nipple from inside the cooler.
Step 6: Secure the FPT barb to the exposed end of the pipe nipple from the inside of the cooler; tighten to the point that the valve doesn’t wiggle when you open/close the lever, just be careful not to crack the cooler.
Step 7: Place 2 hose clamps onto the braided hose, insert the threaded end of the plug into one end of the hose and secure with a hose clamp, then place the open end of the braided hose on the barb and attach with the second hose clamp.
Here’s the exact order everything should be in from the outside in:
MPT barb -> valve -> nipple -> 2 washers -> o-ring -> COOLER ->
grommet -> o-ring -> 1 washer -> FPT -> SS braid -> plug
That’s it, you’ve just constructed the same mash tun I use. Pretty simple, but it does require quite a few parts. One option that might save you $15-20 is using brass components. Probably the simplest and most cost effective approach involves squeezing 2-3′ of 5/8″ vinyl tubing through the hole in the cooler wall, attaching a plastic valve to the outer tube with a hose clamp, then attaching the stainless braid to the tube on the inside of the cooler. The pressure created from squeezing the 5/8″ tubing through the 1/2″ hole is enough to plug leaks, then all you have to do at the end of your mash is open the valve to collect your wort. To plug the open end of the braided hose, people have had success folding the end over itself multiple times. So the order would look like this:
Vinyl tube -> COOLER -> grommet -> braided hose
Whichever way you go, the final result will be beer. Amen.
Please leave any questions in the comments section below and I’ll address them as soon as I can. Cheers!
73 thoughts on “MLT Cooler Conversion”
This is almost exactly my mash tun (mine’s the 48 qt version.) Works great, don’t hesitate.
What is your dead volume\liquid left after run off? Do you just tip the cooler to fully drain?
I have my deadspace in BeerSmith equipment profile set to 1/8 gallon (.12). I do place a 2×4 under the back end of the MLT just to hurry things along a bit.
FYI, your link for the o-rings is wrong, it takes you to a 1 3/4″ ring, not 3/4″
Jeez, sorry about that. I just fixed it. Thank you!
Do you batch sparge with this setup?
Batch and no sparge, absolutely, works great!
Other than price is there a care or maintenance difference between brass and SS valve parts?
Truthfully, I doubt it. One of my MLTs has some brass parts, it still makes the same quality beer as my SS MLT.
Sold, brass it is then.
u don’t have any problems with the braided hose? I ear that manifolds are better… I ear some stories of the braided hose crushing under the weight of the grain.
One of my hoses is over 3 years old, it’s filtered well over 100 batches of beer, recently high OG RIS, and it’s still going strong. I’ve never experienced a crushed hose.
Nope, been using this design for months with no issues.
Thanks for sharing. FYI, your link to the Plastic Valve takes you to the previous link for the Vinyl Tubing.
My pleasure, and thanks for heads up, the link is fixed.
Is it worth adding a built-in thermometer?
I guess that’s up to you, though I’ve personally no interest in doing so. I shut the lid at mash temp + ~0.5°F and typically only lose 1-2°F over the course of an hour long mash. A thermometer probe or thermocouple would only get in the way while mashing in 🙂
I’m just getting into all grain brewing. Where I am in Memphis, the ambient temp ranges from 100+ in the summer to the occasional teens in the winter ( I have to brew outside). I’m trying to figure out the best mash tun set up for the system I’m putting together. Just as a reference point, what kind of ambient temps do you have that you’re only experiencing a 1-2 degree mash temp loss? Mainly for winter time where I am, I’m considering finding a used/scratch and dent rotomolded style cooler for mashing ( new the’re absurdly expensive). But if you only lose a degree or two even in cooler ambient temps, a much cheaper coleman might be a ok.
Is there a reason you use this type of cooler versus the round, stand-up Gatorade type cooler? Is one better than the other for standard 5 gallon batches?
I guess the biggest reason is I often brew 10 gallon batches, which this cooler makes a bit easier. Also, I believe my 70 qt rectangular cooler is less expensive than that 40 quart cylindrical equivalent.
Great article. Thanks for sharing your very thorough write-up. I intend to use this. Also thanks for the links on where to purchase parts.
Thank you for the support!
I am looking into building a larger cooler for my 10 gallon batches and want to use the 70 quart cooler you have. With that being said, I am looking into the new bulkheads the brew hardware sells. Would this work work? Just a thought since I was going to order some other parts.
Looks like it’d work just fine.
Im having a hard time getting the nipple through the cooler. Should I force it through? Also, I don’t think the nipple is long enough to attach the female barb inside the cooler. Im using a Coleman Extreme 62 quart cooler. I hope that made sense. Great site by the way!!!
I would imagine all Coleman coolers have the same size hole, so if you bought the right size nipple it should fit. What I do is remove the white grommet, squeeze that around the nipple, then squeeze it back into place. This has never been problematic for me, though it should fit tightly.
Thanks for the compliment. Cheers!
I encountered a similar problem, i had to go to a longer coupler and then still thread the barb on the first couple threads and pull it the rest of the way through. I think the design of the cooler changed at some point because in addition it this, my heat retention is terrible.
I saw in another post that you really loved the Brew Bag. I was thinking about ditching the braided hose that I’ve been using for years to try out the Brew Bag. Since you’ve used both what do you think?
I’ve fully converted to using Brew Bags in my MLTs, it’s great!
Fully Converted?
Like you use the brew bag exclusively, instead of the ss hose?
That’s how do it now, (with a wilserbrewerbag) but the bag clogs my bulkhead where my manifold used to attach.
Yep, I’m fully converted to MIABIAC (mash in a bag in a cooler), it’s great. There are a few options for eliminating the clogged bulkhead problem, one of which involves reattching your old braid, though I plan to snag some SS elbows soon.
After a mash, do you disassemble your valve from the cooler for cleaning? If not, do you have any good tips on cleaning in place?
I have recently moved to all-grain and had to get valves for my brew kettle and for the mash tun. Didn’t know if i would need to disassemble every time after a brew or if there was another way.
Thanks for the great writeup.
Hi Jeremy, since swapping out my 3-piece valves for the quick clean take-apart valves, yes, I do disassemble them after every use.
Hello. I just built a MLT using the same 70 quart coleman extreme cooler you use, and followed the exact same build. I used a 1/2in full coupler and bought a bazooka tube instead of the stainless steel braided hose. I tested it out today with filling it with water and noticed it leaks a bit outside under the ball valve. Not a lot but a few drops a minute i would guess. Is there anyway to prevent this for happening? Maybe I fastened everything too tight?
Hey Dominic, the drips could be caused by any number of small issues. I tend to crank my shit pretty tight, though perhaps you went a bit too tight. It could also be that your washer on the inside is being propped up by the bottom of the cooler, which if this is the case, you might try removing it and relying solely on the o-ring. Ultimately though, after a few brews, enough sticky wort will get in the cracks and likely seal any small leaks. Sounds gross, but it happens and has no impact on the resultant beers, at least in my experience.
Ah that’s good to know! I did crank things pretty tight, so maybe that could be it. Thanks for the reply! Another question abut cleaning. Do you tend to break all the hardware down and wash/sanitize everything in between each mash? Or since it’s pre-boil, does that not matter much? Thanks again for the great info on the MLT cooler conversion!
The only time I take my MLT apart is when I need the coolers to pack Coors Light in for camping, and even then, they’re not really that dirty.
I wanted to warn your readers: the washers you have linked here have an ID that is about .02″ too small to get past the threads on the linked nipple. You can’t even really force it down either. I’ll be damned if I’m going to buy more washers so I’m going to just try to polish the inside of the washer, but folks should know.
That’s a huge bummer! I bought all of the same stuff listed on the page, it worked fine, and this is the first I’ve heard of this problem. Sounds like you’ve decided to ream the inner hole out, which I’m sure will work, but I wonder if the issues isn’t a mis-sized nipple. Either way, sorry you have to deal with this.
Oh well, crap happens 🙂
I just wanted to recommend that for any of your readers who decide to buy a nipple online that they wait until they actually get the nipple so they can measure it before they buy any washers. For reference a 7/8″ SS washer would fit for the one I received but 3/4″ is just a little too small so that’s an option.
1/2″ NPT pipe/nipples are actually 0.840″ outside diameter. 3/4″ nominal washers have a 13/16″ / 0.8125″ inside diameter. So a 7/8″ (15/16″ / 0.9375″ ID) washer should do the trick.
Dang, same problem for me too – did polishing the washer work for you? Cheers!
Just curious if anyone has done this same conversion on the Coleman 48qt Hardshell cooler. http://www.amazon.com/gp/product/B0000DH4LT?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
Seems like it should be the same at the 70qt, but I wanted to make sure before grabbing the hardware.
Actually, that was the first cooler I used then transferred the valve unit directly to the larger cooler.
Awesome. Thanks for the great post on this build. Will be getting to work on it this weekend!
Hey. How does 48qt mash tun work for you? What batches do you typically brew? I typically brew 5 gallon batches, sometimes smaller, was thinking of new mash tun and just can’t decide what cooler to buy… 5 gallon cylindrical for bigger beers is just not enough based on BeerSmith, 10 gallon is more expansive so I was seriously thinking of this 48qt Coleman cooler. However I am not sure if it’s just not too big for 5 gallon batches given that depth of grain bed is important too in mashing… any thoughts?
Marian- I have a 70qt cool so that I can brew up to 10 gallons. To this point, I’ve only made 5 gallons at a time and its works great.
Not sure how you got a 1/4″ ss braid onto a 1/2″ barb but it is proving quite difficult.
Edit that…it’s a 1/2″ ss braid…whoops. It’s what I had on hand. Looks like I’ll be buying a new ss braid.
Any idea what the diameter of the hole is on your cooler? Brew Hardware sells a True Weldless Bulkhead with two options: 13/16″ hole w/ standard o-ring; 7/8″ hole w/ flat gasket. I’m not sure which option will work. Thanks!
Hmm, I’m not sure. I bet if you email Bobby, he’d be able to tell you the right one to get.
Thanks Marshall, I just emailed him. I read through your instructions again and noticed you wrote this in the paragraph under the last picture: “The pressure created from squeezing the 5/8″ tube through the 1/2″ is enough to plug leaks…” So maybe you did measure it?
Do you recall how tight of a fit the 1/2″ nipple was in the spigot hole of the cooler?
With the rubber washer that’s already on the cooler, the nipple fits rather tightly.
Marshall, with the MIABIAC method, do you just lift the bag and squeeze, similar to BIAB or do you drain and sparge still? I currently use The Brew Bag in my keggle and am thinking about moving up to the cooler for bigger batches as I have to mash with ~8.5G of water now for a 5.5G BIAB batch due to my boil off rate.
No sparge lift and squeeze FTW!
Ok, thank you for the response! Going to go this route too, I love the efficiency and speed of my process. Now on to pick up more equipment!!!
Thank you for your time and devotion to this site, it is very helpfully and saved me a lot of time getting started. Do you recommend still having something attached to the valve on the inside of the cooler to avoid clogging?
Not necessary, but it can help avoid easy to fix bag clogging drain.
How is this any different than BIAB in a kettle? I have a 44qt kettle that I currently do BIAB in, only get 60-65% efficiency though. Is this just giving more space to mash in, are you doing full volume mashes or “standard” water/grain ratio mashing?
Insulation and volume.
I just got all of the parts to make this MLT and unfortunately had to buy the washers, o-rings, and hose clamps in bulk from amazon. If anyone wishes to build this MLT and wants to save some money, I have 90+ o-rings, washers, and hose clamps I am willing to send for a dollar plus shipping.
That’s awful kind of you!
Hey Joe – Do you still have the o-rings? I’d take some of those off your hands if you do.
I am currently converting to All Grain and decided to go with the MIABIAC setup with no sparge after reading your website and doing some research. With that I have a couple questions I was hoping you could answer. Do you mill your grains much finer with the fabric filter and if you do so do you change grain absorption on BeerSmith to match that or leave it at the typical absorption rate for BIAB? I was thinking that if you are milling finer then there would be more absorption due to more surface area. Love the website keep it up!
Hi Jake,
I do mill finer using The Brew Bag, though I haven’t found that to impact grain absorption; rather, make sure to change your absorption rate if you squeeze the bag, which I do… I actually think the BIAB setting in BeerSmith is all I use and it works fine.
Hey Mark, yes I do! Message me here with your info: joefkushner@comcast.net
I have the same cooler that I use for a MLT. I was 9 brews in and it was working great, very reliable and had zero’d in my settings via BeerSmith. Two brews ago I started using a MIABIAC and my wort has been clearer than ever but my gravity has been low. Looking through my settings and outputs everything seems OK, I’m getting my preboil vols I used to pre-MIABIAC. I’m thinking it’s the crush of the grain…anyone else have a similar issue when converting? No grain crusher so I’m thinking about pulsing what I have still in a food processor…
For those looking to combine this conversion with the BIAB, I’ve got a couple of modifications I’m going to try:
– Using a 1/2” Ss locknut on the inside rather than a barb, providing a 1/2 hole out.
– Using a Ss scrubby http://a.co/9NVRNqX tucked in front of the port on the inside, so when brew bag and mash are on top it’s held in place providing flow through while not allowing the mash/bag to completely block/clog wort on the way out.
– Bonus tip: I’ve used Ss scrubbies with great success in my boil kettle, wedged under a pickup tube, so it provides hop/trub blocking power without clogging! The wort must flow….
I just tried this build with a 52 quart Coleman Xtreme, which presumably has walls that are the same (or even thinner) than the 70 quart model in the article. Nevertheless, the 1-1/2″ long nipple was nowhere near long enough to go through the wall and provide adequate exposed threads. I happened to have a 2″ (brass) nipple from a previous build, so I used that for the time being. I have a hard time believing that a 1-1/2″ nipple worked in the original.
Same problem for me. Also, the washers listed did not fit the nipple for me either.
FYI the newer 70qt extreme requires a 3” nipple as opposed to the 1 1/2” nipple. The wall is 2” thick.
Forget what I said about the 3” nipple. It’s too long and doesn’t work.
Picked up 2” nipples with threads the entire length from brewhardware.com worked perfectly.