How do I get 6 gallons of wort from a 5 gallon mash tun?

[speckswme]

I was just given an old beer keg and want to convert it to a boil kettle. The problem is my mash tun cooler is 5 gallons and is max'd out with 3.75gal H20 and 12.5lbs of grain. I use a 5gal rubbermaid cooler and do a single infusion mash and 1 sparge.

My first runnings are usually around 2.25gal, i then sparge with 2.25gal to get 4.5gal which is all my old boil kettle could handle. After boiling i'm left with about 3.75gal of fermentable wort. This means I have to add water to get 5 gallons and I don't like doing that.

How do I get 6 gallons of pre-boil wort from a 5 gallon tun?
Can I double sparge and do something like;
2.25gal of first runnings
sparge with another 2.25gal
sparge again with 1.5gal to get 6 gal?

or

collect 2.25gal first runnings
sparge with 3.75gal to get 6gal?

Trying to figure it all out.

Thanks for your advice!!

 

[jakenbacon]

Well, after your first runnings, the grain is saturated with liquid, so it will not absorb any more liquid you put in after the fact. So to make the math easy, if you pulled 2.25 gallons off initially, just sparge with 3.75 gallons (yes I know, your max) and you should receive all of that 3.75 gallons back from the tun giving you your 6 desired gallons. Better to do one large sparge than 2 smaller ones so you don't extract tannins (assuming you dont have your PH in line yet that is)

 

[Kingbogart]

Based on your process it sounds like you are batch sparging. I know many people that do multi step batch sparge and it shouldn't be an issue to split it how you mentioned above.

Also, based on your numbers, you could potentially try to fly sparge. 3.75gallons and 12lbs would put you right at 1.25qt\lb which is about what I generally mash at. Then you just continue sparging until you have collected what you need. The speed out is the same as the speed in, so overflow shouldn't be an issue. It is pretty close on the split for fly sparging as well, since many people suggest 1/2 your water for mash, and 1/2 for sparge. You would be around 3.75 and 3.57 assuming 1.33 gallons of absorption to grain.

 

[Yooper]

You are limited of course by the size of your mashtun to about 12 pounds of grain or so. That means you can make a 5 gallon batch of about 1.065 OG or so, without needing to add any DME for a higher gravity.

There is this calculator here http://www.rackers.org/calcs.shtml called 'can I mash it?' (scroll down a bit) and you can put your grainbill in and see if it will fit in your mash tun. Not accounting for the false bottom, you can use 12 pounds of grain and 1.33 quarts of water per pound of grain, and it will all fit.

So, you'd add nearly 4 gallons of mashing liquid and 12 pounds of grain, and be ok.

Out of that mash, you'd get about 2.5 gallons of first runnings out of the MLT. You can then sparge up to your boil volume, with no worries.

 

[speckswme]

@Jakenbacon, that was my initial idea but then became concerned that it may affect my efficiency? Is that possible? My first two AG batches i had a 66 and 69% efficiency.

I don't have any idea what my ph is yet, should I?

Adding 3.75gal as my sparge amount would be the easiest for me but would it be the most efficient?

 

[Yooper]

@Jakenbacon, that was my initial idea but then became concerned that it may affect my efficiency? Is that possible? My first two AG batches i had a 66 and 69% efficiency.

I don't have any idea what my ph is yet, should I?

Adding 3.75gal as my sparge amount would be the easiest for me but would it be the most efficient?

You should try to consider mash pH. It's important, not just for conversion and efficiency where it plays a tiny part, but for flavor. Knowing your water profile is a good way to get started.

Your efficiency won't be affected by one batch sparge vs two, or fly sparging, in any meaningful way.

 

[Hoppity]

You could do a partial mash and add DME or steep a bag of grains in the Boil Kettle prior to the boil. That way you can boost the sugars in the BK to hit your target pre-boil gravity. Mash out/sparge to your pre-boil volume.

 

[speckswme]

So I think as long as doing one big sparge with 3.75gal doesn't have a negative affect on my efficiency, ill do that.

Thank you!