Hot Liquid in Mash Tun Water Cooler

I’ve been planning to dip my toe into the world of all grain brewing and have made an interesting discovery about using a water cooler (like what Rubbermaid makes) as a mash tun. It seems that the “company line” is that the water cooler shouldn’t be used for liquids over 120 degrees.

Clearly lots of people are mashing in such a cooler, and the coolers made under the Fermenters Favorites line look pretty similar with regard to construction.

Is there such a thing as a plastic mash tun that’s “officially” supported for hot liquids, or are we all just choosing to go with it because in reality it works?



I use an Igloo water cooler. Changed the guts and it works for me. I preheat the cooler with 170-180 water.


I use the fermenter favorite. Seems to do well… I wish I had have went the way of igloo for money sake. The FF brand was pricey. But the set up did come with all the hardware and 2 false bottoms.

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I don’t know of any food grade rated for hot liquids.

Sadly, I never thought of this question 15 years ago when I started using my cooler mash tun.

I figure that now, all the Chinese mercury has leached out into my beer/liver. My cooler tun is probably food grade by now. I just hope I don’t get cancer someday from all the unknown chemicals it has caused me to imbibe.


Brew in a bag. In your stainless kettle. Problem solved.


I’ve been using a Coleman Extreme cooler for my mash tun, seems to work just fine. I’ve noticed the lid warps a little by the end of the mash, but after it cools, it straightens back out. I use a Rubbermaid for my hot water tank and it’s fine for the whole like 15 minutes that the water is in it (which is all I need it for). I did find out the hard way that the drain plugs they put in them soften and deform easily. Once I removed those and replaced it with stainless, I’ve had no issues. Between both coolers and the fittings, I probably have a little over $100 into it all and I’m happy with it. The Coleman has an anti-microbial plastic and I’ve found it incredibly easy to clean.

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In almost 40 years of legalized home brew, I would expect it would be common knowledge if coolers leached anything toxic at mash temps. Hell, @denny’s continued survival proves mashing in coolers can’t kill you. :slight_smile:

They probably recommend against using the cooler for hot because it may leave a plastic-y flavor in tea or coffee that boils off in wort when you boil it after being in the cooler.


I use to enjoy the way it would contort! SS doesn’t…. just kinda stays put, never changes, ever. Sneezles61

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Coolers are made of HDPE. Completely harmless at mash temps.


I’ve seen some coolers where the foam insulation expanded due to high temps. That was 20+ years ago. I think they discourage hot liquids to prevent any warranty replacement issues.


Thanks to all who have responded! This is all very helpful!!