Mash Tun Question...

[SoilKnurd]

Fair warning.... I read the entire thread of the sticky "This is how big your Mash Tun needs to be" and still have some questions.

So here's where I am... A couple of friends and I jumped straight into AG and tried a really big IPA (The Stone Enjoy By recipe posted by scottland). We brewed a double batch, and things went pretty well. We're on the last dry hop and are gonna be bottling in a few days. Go big or go home, right? We had some borrowed equipment, and lots of help from a seasoned veteran home brewer friend from afar.

We have a fair bit of equipment, but borrowed a mash tun for this batch. We're wanting to build one, are planning to batch sparge, and want to build a copper manifold for it. We're planning on doing 10 gallon batches normally, but want to have the flexibility to do 5 gal. I think I've narrowed it down to two cooler styles, the Coleman 70 qt (interior dimensions 24.5" x 10" x 14" high) that many folks recommended on the sticky, and something more squarish, like this Coleman 75 qt. (inside dimensions 11" x 17" x 15.5" high). Here are my questions:

1. I know that you need an adequate grain bed depth (IIRC, Palmer mentions min 4" for batch sparging) to produce clear wort. If we're doing a big 10 gal batch, the 70 qt is plenty sufficient. If we're doing the same in the 75 qt, is the bed going to be too deep? If we're doing a 5 gal batch, will the 70 qt be to shallow? I know most folks say that grain bed depth doesn't matter for batch sparging, but that's hard to totally believe... there must be limits to this.

2. The 70 qt is nicer since you have more room to be able to stir. Is there any other reason the 70 wins over the 75? It would seem that the more squarish one would be better as far as heat retention, due to a smaller lid surface area and shorter length of where the lid contacts the body of the cooler.

Is there anything else I need to be considering?

Sorry for the long post, and sorry if these questions have already beed answered. Thanks for the help!

 

[SoilKnurd]

Ok... I really thought you guys would jump all over this. Nobody has any thoughts?

 

[Yoseff]

Personally, I like the round coolers more than the square ones for mash tuns. Less chance of dead space. As for the size issue, I'm going to have to defer to someone else.

 

[LandoLincoln]

Clarity of wort is...well...it shouldn't be high on your list of priorities. I have a recirculating mash system and going into my BK my wort is crystal clear and that makes me smile, but I'm not trying to fool myself into believing it makes any real difference in the final product.

You're trying to equate batch sizes with cooler sizes and you can't really do that. You should be equating grain bill sizes with cooler sizes.

Grain takes up about .32 quarts per pound of grain in the mash tun, volume-wise.

If you assume 1.5 quarts of strike water per pound of grain ratio...

You could fit 38.5 pounds of grain into a 70 quart cooler. 38.5 lbs of grain * .32 = 12.32 quarts taken up by the grain, plus 57.75 quarts of water = a grand total of 70.07 quarts.

You could fit 41.25 pounds of grain into a 75 quart cooler.

If you went with a thicker mash (1.25 quarts)...

You could fit 44.5 pounds of grain into a 70 quart cooler.
You could fit 47.75 pounds of grain into a 75 quart cooler.

38.5 pounds of grain is a very large grain bill for pretty much any 10 gallon batch of beer.

Your typical PPG of regular 2-row is about 31 (average yield), so if you had 38.5 pounds of 2-row you could yield around 1,193 GU's. 1,193 divided by 11g is a beer with an OG of 1.108. Wow. Even throwing in less viable malts like roasted barley and whatnot you could still easily make 11g of a 1.090 batch. And that's with a relatively thin mash.

So what I'm trying to say here is that for an 11g system the 70 quart mash tun is more than enough. Way, way more. Unless you're really into barleywines.

Your biggest problem would be dead air space in your mash tun. Lots of dead air = lots of heat loss.

 

[feinbera]

If you're batch-sparging, don't worry too much about the shape – you should be "stirring like you owe it money" before you run off, which should redistribute the sugars even from the farthest corners evenly throughout the tun.

In fact, I'd even reconsider the copper manifold, in favor of a stainless braid/bazooka screen or a false bottom, so there will be fewer spots you won't be able to get your mash paddle into. You don't have to worry about channeling if you're batch sparging, and even if you plan on upgrading to fly in the future, bazooka screens are cheap and stainless braids are cheaper.

 

[LandoLincoln]

Stainless braids / bazooka screens are the cause of more stuck sparges than any other type of draining system. I'd rather suffer a consistent 5% efficiency loss than ever have a stuck sparge ever again. Screw those braids.

 

[SoilKnurd]

Thanks guys! I know we should get two tuns for different batch/grain bill sizes. Just trying to maximize the bang for the buck. I doubt we'll go much higher than 1.100. I definitely don't want to have to deal with stuck sparges, so I think we'll go with the manifold. Lots of folks are suggesting the round Rubbermaid coolers, and that's what we'll likely ultimately go with for 5 gal batches. I hear ya that it's more a matter of grain bill size than batch size. But you still need a cooler larger than your batch size to fit all the grain and strike water.

The beer we just bottled had a 33 lb grain bill, so I guess the 70 qt should do us just fine. If we start ending up with lots of dead space in the cooler, we can always try the aluminum foil or foam insulation trick that others have suggested. And once we really get going, we can dial in our system to know what losses we're getting.

 

[hottpeper13]

My tun is the Coleman extreme 62 qt with wheels. Because of the wheels there is a shelf inside that makes for very efficient 5 gal batches. It holds 31 lbs of grain but I have to decoction mash to get to mashout temps. The best feature is the drain hole,it's lower than the floor and kinda channeled. With a bazooka screen there is only about 4 oz of water left after tested for leakage. In order to get above 80% I do need to add rice hulls.

 

[brewfarmDan]

Stainless braids / bazooka screens are the cause of more stuck sparges than any other type of draining system. I'd rather suffer a consistent 5% efficiency loss than ever have a stuck sparge ever again. Screw those braids.

Just getting ready to build one with braid and had not heard of the problem with stuck sparges. So you recommend a copper manifold? What size? slotted with a saw blade? Do you have a link on how to build, most of my searches came up with braid. Thanks Dan

 

[Clankenbrew]

IMO.. I would get more than the 70. I have a 70 and 120. The 70 is too close to the top for me when doing big beers. Its very messy.

 

[Clankenbrew]

Also.. Removed my bazooka tube and replaced with copper manifold after too many stuck sparges

 

[LandoLincoln]

Just getting ready to build one with braid and had not heard of the problem with stuck sparges. So you recommend a copper manifold? What size? slotted with a saw blade? Do you have a link on how to build, most of my searches came up with braid. Thanks Dan

I'd actually recommend a manifold made out of CPVC and drill two rows of holes near the underside of each pipe. CPVC is safe for hot water, is a lot cheaper and the fittings stick together better than copper when they're not glued/soldered.

Lots of pictures available on Google image search for "CPVC mash tun manifold"

 

[SoilKnurd]

Hmmm... 120 qt seems a bit large... What's the preboil volume/OG of the beers you're mashing in that cooler?

I hadn't thought of CPVC... That certainly would be cheaper.

Palmer's book details the best way to design a manifold. I'm a noob, and have really enjoyed his writing style, how informative he is, and how he seems to back up his info with science.

 

[Clankenbrew]

Hmmm... 120 qt seems a bit large... What's the preboil volume/OG of the beers you're mashing in that cooler?

I hadn't thought of CPVC... That certainly would be cheaper.

Palmer's book details the best way to design a manifold. I'm a noob, and have really enjoyed his writing style, how informative he is, and how he seems to back up his info with science.

Usually about 18-20 gallon preboil..
I've only used it twice, once for big 12% stout and once for a 10% Double IPA. . Im running a RIMS system so headspace is not a problem using this one.
Getting rid of the spent grains a big problem for me

 

[SoilKnurd]

Yeah... I have a keggle, so that kind of preboil volume is a deal breaker.

 

[SoilKnurd]

Spent grains being your biggest problem is a good problem to have

 

[SoilKnurd]

So we finally finished the mash tun. We ended up going with the 70 qt Coleman and a copper manifold. The slits were cut by hand with a hacksaw... It is a lot of hack-sawing, but the copper cuts really quickly. We tried using a sawzall/reciprocating saw, but it didn't work well. We also tried a Dremel tool with a cutoff wheel, but that was pretty slow.

Here are some pics of the finished product.
View attachment ImageUploadedByHome Brew1434134279.703238.jpg
(I know the slits need to be down when in use... They're just turned up for show)

View attachment ImageUploadedByHome Brew1434134371.466772.jpg

View attachment ImageUploadedByHome Brew1434134387.299813.jpg

We ended up having to shave off some of the tees where the three tees come together near the barbed fitting for the outflow from the manifold. The tees themselves were too big and they all wouldn't fit in our spacing (we didn't think about that in our design[emoji53]).

The tubing is 1/2" copper, and the spacing is as Palmer suggests in his book.

We used it for the first time recently to brew a hoppy blonde ale. The manifold worked like a champ, but the bulkhead fitting wanted to leak a bit. Anybody have any thoughts?

 

[stpug]

the bulkhead fitting wanted to leak a bit. Anybody have any thoughts?

Teflon tape to seal between the nipple threads and locknut. You should only need rubber gaskets between the locknut and cooler wall on the inside of the MLT; the outside should not need any. Looks really good.

 

[SoilKnurd]

Ok... We did the Teflon tape, which helped a bit but didn't totally seal it. I guess we were screwing up by putting a gasket on both sides of the cooler wall. I'll try it with the one in the inside.

Thanks!