DIY Mash Tun Build – Parts Shopping List

by Daniel on April 9, 2012

finished build of my MLT

You’re ready to take the leap to all grain, and here I will show you step by step how to build a 10 gallon mash tun from a cooler.  While you’ve been considering converting to all grain brewing, you (like me) may have been intimidated by the idea of the new equipment required.  Hopefully after this post I’ll have you convinced that learning how to make a mash lauter tun is easy to do, and cheap as well.  The next post I’ll walk you through the assembly.  I’ve done all the research and shopping around for you.  The main thing that you need to convert to all grain brewing is a vessel to hold all the grain while you do the mash, and then something to let you drain away the sweet wort and leave the grain behind.  This project was by no means my own idea–it is mentioned in many places, including John Palmer’s book How To Brew in the appendix, and online in the HomeBrewTalk forums.  I thought I could make a few things a little clearer in some areas to make it as easy for you to do this yourself as possible.  One quick thing you should know – it really is worth it to build a 10 gallon mash tun rather than building a 5 gallon one, although these parts will work for both.  I’ve put in two options for the build: one with a false bottom you build from a braided stainless hose, and one with a pre-fab false bottom for purchase.  Let’s get shopping!

I chose to design mine with a circular “false bottom” to work as the filter, made from stainless steel braid taken from a faucet supply line.  Other designs have a simple straight piece rather than doing the circle.  In my reading & research I found that the circular design provides better draining, less likelihood of a stuck sparge, and it better distributes the weight of the grain when the cooler is full.

Shopping list (by store name, updated most prices as of Feb 2013):

Home Depot or Lowes (see picture to right):

brass parts soaking in vinegar/hydrogen peroxide mix

  1. 10 Gallon Picnic Cooler ($45) – I got a 10 gallon Igloo on Craigslist for $25.  Rubbermaid is another brand.
  2. Get 2 of the: Watts A-298 (part number, in plumbing section) – Hose Barb Adapter – 3/8″ Barb x 3/8″ FIP (female) – $3.40 ea
  3. Watts A-294 – Hose Barb Adapter – 3/8″ Barb x 3/8″ MIP (male) – $3.12
  4. Watts A-786 – Brass Pipe Nipple – 3/8″ MIP x 1-1/2″ – $3.40 – in later pictures – the piece that passes through the hole where the spigot is removed from the cooler.
  5. Watts A-168 – Flare to Flare to Flare Tee – All 3/8″ – $5.11 – second from left of picture
  6. Watts A-760 – Coupling 3/8″ FIP – $4.47 – far left of picture
  7. 3/8” threaded ball valve – $8.21 – with red handle in picture
  8. 30″ Stainless Steel faucet supply line 1/2″ diameter – $8.49 – I actually got the guys at Home Depot to cut the ends of this off for me with a hack saw since I don’t own one myself and you need to do this for the project.
  9. 4 x 5/8” fender washers  (or flat washers) – $.35 ea
  10. **3-4 smaller outer diameter washers (still need at least 5/8″ inner diameter)** if you do the Home Depot or Rubbermaid cooler – this is because there is an indentation in the plastic on the outside where the picnic tap comes out, so you need some to fit this smaller area in order to get a good seal.

For all of the Watts parts above, the packages can be seen in a picture below.

10 Inch Stainless False Bottom

10-12 Inch False Bottom

UPDATE: If you want to purchase a stainless steel false bottom rather than use the braid I describe below, you need one that is 10-12 inches in diameter (measure your cooler first, the one from Home Depot can fit the 12 inch).  One of the best deals I’ve found is from ($31 compared to $40 elsewhere).  I have actually switched to this myself, and I absolutely love it. My Igloo fits the 10 inch.  It’s a great filter, and it also doesn’t get displaced when stirring or get damaged over time.  In this case, you still need to purchase everything below except the cable ties, but only the following parts from above: Watts A-294 (get two instead of one), A-786, A-760, the ball valve, and fender washers).  If you do the math, you save about $17 in misc. brass parts, and replace that with a $31 stainless false bottom and a bit of 3/8″ ID clear hose.  Only a $13 difference makes this a lot more reasonable than I thought when I first was looking around!  If you decide to continue with the stainless braid from the supply line, that’s fine too.  The rest of the parts are below for either method.

ACE Hardware (or other small hardware store where you can find these as single pieces rather than buying a pack at Home Depot and thus overpaying)

more parts for mash lauter tun build

  1. Plastic 8″ cable ties (20 count) only need 4 – $2.79
  2. 5/8″ black rubber grommet – $0.90 – Even if your cooler has a grommet already, you may need this in addition if the grommet doesn’t seal both sides of the hole where your tap is passing through.


  1. 5/8″ Inner Diameter (ID) Stainless Steel washer (see above photo)- $1 – this can be very tough to find (as others online agree) – It is important to have this one in Stainless because it is going to be in contact with your mash and you don’t want metal ions from nickel plated, adonized, or whatever other kinds of washers might have getting released into the wort (needs to be “food safe”).  I ended up getting mine at a local auto type parts shop (non-chain) called Herb’s Fastener & Supply.  Definitely call a place before you show up looking for this part – it’s tough to find and you can save yourself driving all over by calling.  Let me tell you places I called or visited that DID NOT have this part so you can start looking at other places: Home Depot, Lowes, Ace Hardware, True Value, Pep Boys.  Usually these stores have SS washers, but only up to a max of 1/2″ ID, and you need 5/8″ ID.
  2. Teflon tape to wrap threads for a good seal.
  3. Keg Lube/Petroleum jelly – I put some of this on my grommet so I could slide the brass nipple through easily.
  4. Hydrogen peroxide & vinegar – many people have this lying around the house.  The purpose of this is you make a mix of hydrogen peroxide & vinegar 1:2 ratio and soak all the brass parts in (that’s what’s happening in the picture) in order to remove trace amounts of lead and such.  This is described by John Palmer in his appendices section.  It isn’t completely necessary and you’re probably not going to get lead toxicity if you don’t do it, but I did it, and it only needs to be done once.

Now you have all the parts you need (I got all mine above for about $83 thanks to saving on the 10 gallon cooler), here is my next post on how to assemble your mash tun.

Check out my other easy DIY projects here, and subscribe to my blog with your email on my side bar for updates!

{ 16 comments… read them below or add one }

Ryan Hollis May 10, 2015 at 4:51 pm

Why do you use a 5/8″ ID grommet with a 3/8″ nipple? seem like to me that it wouldn’t be snug, but it appears snug in the pictures. Are these pieces true to size?


Daniel June 2, 2015 at 12:04 am

Hi Ryan, thanks for noticing this! This grommet is listed as 5/8″, but I think that’s actually the outer diameter. Either way, the one I link to is what fits the hole of the cooler when you remove the plastic tap.


Ryan February 26, 2015 at 1:30 pm

Hi Daniel. I just got all the parts including the 10″ SS false bottom. With a 10 gallon cooler the bottom looks way too small. Can you explain how it woks and what it rests on? I measured the ID of the Lowes Igloo cooler I got and its 13″. I am wondering if I got the wrong size bottom. Thanks


Daniel February 26, 2015 at 10:25 pm

Hi Ryan, thanks for bringing this to my attention! I have updated my post to correct this issue. It works by connecting the barb with high temperature tubing to the barb going out the ball valve. It rests directly on the bottom of the cooler, no need to secure it as the weight of the grain will hold it down. The good news is even the 10″ size will probably serve just fine. If you think about the stainless braid loop design that I also describe, it does not span the entire exact circumference of the cooler, nor does it necessarily rest fully on the bottom of the cooler. Yet it really works great. It’s more about the force of the liquid above sifting through the grain, and channeling through whatever filter there is at the bottom. The flow typically will still find its way through all the grain, regardless of the edges not completely making it around. I’m sure you could probably exchange it without too much trouble though. KegWorks has good customer service in my experience.


Ryan February 27, 2015 at 10:12 am

Thanks Daniel. Maybe a dumb question but when you put the false bottom in the cooler do you put the barb facing up or down?


Rich August 14, 2014 at 12:37 pm

Found 5/8 stainless washers at menards lumber in the nuts and bolts section for 1.59 for a six pkt


Daniel August 19, 2014 at 12:00 am

Thanks Rich!


Shelton October 31, 2013 at 2:42 pm

Daniel, Thanks – this is the easiest and most useful DIY build I found for a mash tun. I found all the parts needed at Home Depot and got the 5/8″ diameter stainless steel washer from my local home supply store without issue. I had a problem with the seal on the rubbermaid cooler however, it was broken. Of course it leaked so I grabbed a silicone baby bottle nipple (obviously food safe), cut the tip off and used it as the seal and it worked perfectly, even making up for a bit of space between the ball valve and the edge of the cooler.


dennis.lifefermented October 8, 2013 at 10:59 pm

Hey Daniel, great write up. One improvement on the standard bulkhead design in most DIY mash tuns I came up with is drinking water safe epoxy instead of a rubber seal. I always had issues with mine leaking after a few batches after the strike water hit it and rapidly changed the temperature. The epoxy molds right to the surface and creates a great seal. Full details can be found over at my blog post:


Daniel October 9, 2013 at 1:41 am

Hi Dennis, thanks for the response. I like the idea of putting drinking water epoxy around for a seal. I haven’t yet had a problem with my seal, but I’ll keep an eye out!


Andrew September 26, 2013 at 9:27 am

Daniel – thank you for this info – I plan on building my MLT today. I also put your supplies list for the MLT into an easy to read format – let me know if you’d like a copy to post on your site.


Daniel September 27, 2013 at 1:05 am

Hi Andrew, I’m glad to hear you’re building it. I’d love to see your easy-to-read list of supplies, it would be great if you could email it to me at


Mat August 7, 2013 at 12:51 pm

Hi Daniel,

I’m reading a lot of people on homebrewtalk’s forums saying that the spigot of the Home Depot coolers that have been in store since Aug 2012 have a large hole for the spigot. Have you had anyone mention this to you as a problem? The builds I see are a bit different from yours. Notably the5/8″ rubber grommet is not included so perhaps that is why people are claiming they can’t get a seal and are consistently dealing with leaks. I am planning on running out and making these purchases this evening so that is why I ask.

Kind Regards.


Daniel August 8, 2013 at 1:35 am

Hi Mat, thanks for the question. You’re right, I recently built one with the Home Depot cooler for a friend, and I bought a second 5/8″ grommet so that there was the original grommet on the inside half, and my new second grommet for the outside half of the plastic, then pretty much everything else works great. Thanks for bringing this back to my attention! I’ll try to update the post soon.


Cansas April 26, 2013 at 10:13 am

My hubby and I built this and used it last weekend. It worked great! Thank you for posting in such detail. BTW, we used flat washers instead of fender washers b/c we couldn’t find those and it was no problem. Not one leak and drained perfectly.


Daniel April 26, 2013 at 6:12 pm

Thanks Cansas, glad to hear it’s working – and thanks for the tip about the flat washers. You’re right, they’re a great substitute.


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