Topping off a biab

[HerkimerBrewer]

Ok, I've been doing BIAB for awhile, lots of batches under my belt. I always seem to have trouble hitting my number for how much wort should be in my kettle after I pull the bag out. I've tried all different kinds of calculators.
I'm wondering if it would work if I purposely shoot low, so end up with 5 gallons in the kettle, and then top it off with water to get up to 7 everytime.
The last one I did I was trying to get 4 into the fermentor...ended up with 6 based on the calculator, and the beer is good, but slightly watered down. I use a keggle, boil off is two.
Thoughts?

 

[Jorb]

BIAB typically has a thin mash so less volume of water shouldn't be a problem. If you're doing a super big grain bill you might want a little more water in for the mash, otherwise it sounds good.

 

[HerkimerBrewer]

The other reason I was thinking about it was because awhile back I wanted to do a double batch, and quickly realized that the keggle is not big enough for all the water needed, but would be if I could just top it off.
Usually I'm using around 12-13 lbs of grain.
Can you explain thin mash?

 

[JONNYROTTEN]

I don't worry much about water levels the much anymore. I'm always a little short which is better then to much water.

I just fill up my bucket till the worts gone and add tap water to the fermenter to get to my desired level. Hasn't given me an issue but I have good tap water

Suck up every drop of trub/coldbreak and leave nothing in the BK. Hop bags work good for keeping the hop crud out of the wort

 

[mongoose33]

The other reason I was thinking about it was because awhile back I wanted to do a double batch, and quickly realized that the keggle is not big enough for all the water needed, but would be if I could just top it off.
Usually I'm using around 12-13 lbs of grain.
Can you explain thin mash?

Take two mashes, same grain bill; one has 4 gallons of water, one has 6 gallons of water. The second mash will be thinner, i.e., more water per pound of grain.

I've been doing traditional all grain with a mash tun; typically I mash with 4, sometimes 4.5 gallons of water.

I just did my first BIAB on Saturday, and I started with 7.5 gallons of water. A much, much thinner mash because I had much more water than I typically would mash with.

PS: everything went well, though I had more wort at the end than I would have normally expected. Adjusting next time. Beer is fermenting like it's a house afire.

 

[kh54s10]

The big consideration is what the preboil gravity is with the correct volume. If you have the right gravity but too little wort, adding water will lower your preboil gravity and you should end up with the right volume, but weak beer.

You are doing something wrong in you calculations. Grain absorption is fairly predictable, you should not be getting big swings in volume.

It should be pretty much - grainbill pounds will absorb X amount of water so if you want 4 gallons into the fermenter you will need 4 gallons + absorption + boil off.

The only real variable is how much wort you squeeze out of the grains.

 

[HOPME]

Most online calculators are pretty accurate in my experience as long as you know your boil off rate. Which one(s) have you used?

 

[craigthunder]

I haven't been brewing for too long. I only top off on BIAB if my gravity is higher than I intended. Is this the wrong way to think about it?

 

[HerkimerBrewer]

I'v been using the brewers friend software, I've also tried the one on the screwy brewers website. I've been leaving 1-1.5 gallons behind for trub....does this sound excessive? I don't have a pickup tube, so I do this keg tilting maneuver, but I have to keep the crap out, or the counterflow gets clogged.

 

[Jorb]

It sounds excessive to me for a five gallon batch. I dump all the break material into the fermenter and generally leave about a quart behind in my tubing, counterflow chiller, pump, and what my dip tube leaves behind. I also use a hop sock and whirlpool but can't seem to get the break material to settle before I drain the kettle so it all goes in. If I were leaving the break behind I would lose about a gallon.

 

[Jim311]

Topping off is fine, and if you have warm tap water and a hard time getting to pitching temps, topping off with some ice cold water from the fridge/freezer can help provide you with the boost you need to get down to the temp you need. But what I really think you should do is refine your process enough to know how much you're boiling off and how much your grains are stealing. It's not that hard to calculate yourself, with no calculators involved. Here's my personal formula, for a batch with 12 pounds of grain in a 15 gallon keggle.


I use 7.75 gallons of water total for the batch

Immediately when I mash in the grains steal 1.2 gallons of that water. I multiply the amount of grain in pounds by .1 to calculate the approximate amount.

Then the boil is going to evaporate some water. This is your variable because everyone's setup is different depending on their elevation, the size of their pot, and how vigorous their boil is. Mine is about 1 gallon per hour. I end up with about 5.5 gallons into my fermenter, I drain every bit of trub and everything into the fermenter.


So to recap:

7.75 gallons of water total for recipe
12 pounds of grain x .1 gallon lost per pound = 1.2 gallons lost in mash
Boil off rate is around 1 gallon, calculated by simply measuring total amount in fermenter after all is said and done.

 

[HerkimerBrewer]

I just ordered a whole bunch of ingredients, I'll try this formula next brew day. Thanks for all the input!

 

[hottpeper13]

Jimmy, .11 is what I use for my mash tun, when I went to BIAB the absorption rate went down to .04 because I squeeze the piss out of it. I also have more trub in the kettle then when using a tun.