replacing my mash tun

My current mash tun is on the way out. After about 3 years of faithful service, it is losing heat more and more rapidly each session. In the beginning, it would loose 3 degrees or so over an hour. Now it's loosing upwards of 10 degrees. My method has not changed, so I'm not really sure why all of a sudden my cooler has lost its capability to insulate.

I'm torn between a 5 and 10 gallon round cooler. 95% of the beers I have made in the past 5 years will fit into a 5 gallon cooler, but I'm still leaning toward a 10 gallon MT. My only concern with going with the 10 gallon is the the unused space and any temperature fluctuation caused by said unused space. Seems to me that the fuller the MT, the less heat loss. I make 5-6 gallon batches and rarely do high gravity beers.

Is the unused space in the MT a concern to anyone? Does the partially full 10 gallon MT loose more heat than a mostly full 5 gallons MT? Or is it negligible.

I've only used a 10 gallon round cooler as a mash tun, but I've not found the head space to be an issue. My temperature has fallen between 0-2 degrees during the mash with my 10 gallon rubbermaid round cooler. I live in Florida, so I'm probably aided by the ambient temperatures we have here most of the year.

I mash regularly in a 10 gallon Igloo Industrial round cooler and it loses about one degree over an hour even with a thick mash on a five-gallon batch (read: with a lot of head space). A ten-gallon tun gives you more flexibility in your recipes (you could even do 10-gallon batches of lower gravity brews) and I think the difference in insulating effectiveness is slim to none.

Why a round cooler? I find rectangular easier to use and you get a lot more volume for your money. FWIW, I've used the same rectangular cooler for nearly 15 years and 429 batches and it still works fine.

The cooler I currently have is a square 48 quart Coleman (the one that's on the decline). I had no faults with it until the last few batches. I'm not set on a round cooler. I would go square again if I could find one that fits the bill. The last place I went didn't have a lot of square coolers for sale, probably a seasonal thing. But, they had both 5 and 10 gallon round ones.

Denny- what brand of cooler have you been using for all these years?

Just a cheap Rubbermaid.

I've got a rubbermaid 5 gallon and I haven't found its small size to be a real issue. Obviously if I were going to do a barley wine it might be a problem. The thing holds heat crazy good too.

But hey, if I were building a new one I'd probably go with a 10 gallon, could dump all the sparge water in at once and walk away for a bit.

If your worried about the heat loss you can always prime it with hot water before you use it, but I honestly don't think that extra space is going to make a big difference.

I have always preheated my MT and covered it with insulation or sleeping bags. Not sure why it is loosing heat all of a sudden. I thought the head space may have attributed to some the the loss.

estricklin said:

But hey, if I were building a new one I'd probably go with a 10 gallon, could dump all the sparge water in at once and walk away for a bit.

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This. That's part of the reason I changed from 5 gallon round to 10 gallon round. Not much difference in temp loss. If you are outside in cooler weather, I suggest buying some of that foil bubble wrap insulation stuff from Menards or Home Depot and cutting a pattern that will fit several layers around your cooler. I do this, seal it with a little packing tape, throw a blanket on top, and it is good to go. If it drops really cold outside I slip an inverted garbage bag over it, then the blanket. Plastic really helps it hold the heat in.

Cheers.

You may have water leaking into the insulation of the cooler. That would prevent the cooler from maintaining a consistent temp. I would take the valve out and check for damp insulation and let it air dry.

Hey OP sorry about the MT fading out on you. I have a 10gal Home Depot MT. I do 6 gal batches (w/ the idea to 5+ left over for kegging) and batch sparge. I can't really say I lose any heat during a 60min rest (Head Space not a problem). I also think a 5gal round cooler would be much more difficult to deal with, especially w/ a batch sparge as I typically batch sparge with close to 5 gallons.

Edit: its a round cooler

I never thought about leaking around the valve. It doesn't leak to the outside, so I always assumed it was tight, and there are no cracks inside the cooler. I will check that out when I tear it apart to build the new one.

I brew in my semi-heated garage. But, I'm in western Washington and it's not like we have harsh temps (avg winter temps are 40-50's, probably low/mid 60s in my garage). I use the foil bubble wrap insulation now. Before that, I used sleeping bags. The garbage bag is a good idea. I'll keep that in my bag of tricks.

I'm going to go with a similar size cooler to what I have now (48 quart). Whether it's round or square will probably depend on price because: 1) I batch sparge, and 2) I'm cheap.

Thanks for everyone's input.

I use a 10 gal MT. I have had good results by heating it up ahead of time, prior to the mash. That has always worked for me. Good luck in your ultimate decision and happy brewing

Cheers

I just saw a good price on Amazon for a 70 qt coleman extreme.

Denny said:

Just a cheap Rubbermaid.

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So that's where the magic happens, eh?