This is what I do. Enter 7.5 L into Section W, 'Water Added Before the Boil' and 9% in Section X, 'Adjust Auto Kettle Efficiency by'.

I am assuming the 90 mins. mash and boil and the hopsock is set to 'Y'.

Hey Brandon,

It's been a while since we last talked via PM. As you know, we have the same size keg, that is why we are matching on the BIABacus.

Your first 10 gallon batch, cool. I guess you have a recipe you brewed previously as a 5 gallon?

How many brews have you done with the BIABacus? I repeated a ~9.5 gallon recipe three times in a row. I missed my OG on the first one, it was too high, so I 'adjusted' the efficiency to 6% and it was still too high. I hit my OG on the 3rd brew with it set at 9%. I don't know for sure what efficiency you will get though... , so I am guessing. If you feel better about removing the 9% then do so, okay, and then you can adjust Section W's water before the boil, (YES AFTER MASH OUT), by up to 20% of the TWN value, so that would be about 11.2 L. This might be the safer thing to do.

I think PistolPatch might have said 30% is the max., but in this case 20% will work.

With the 9% and 7.5 L thing, the mash volume is at a minus -0.6 cm, which is fine, as our keggles are calibrated to the welded seam. , still plenty of headspace... You can now see that 10 L before the boil will work also.

Remember to adjust Section D to the new VAW.

Just a couple of clarifications on this one.

Auto-Efficiency

Generally, you should not adjust the BIABacus auto-efficiecncy until you have done several brews as this will keep you safe. Bascially, if your water chemistry, mash temps etc are all good, you should do better than the auto-efficiecny but there is no problem in leaving it alone. The worst that can happen is that you will end up with more beer than planned.

The auto-efficiency should not be adjusted based on OG alone. I'm sure MS only adjusted it because he was not only getting higher gravities than predicted but at least the same or higher Volume of Ambient Wort than predicted. Efficiency is not about specific gravity, it is about specific gravity and volume combined. If we gave two brewers the same anount of grain and asked thenm to make wort, if one ended up with 25 litres of wort at 1.040 specific gravity and the other with 20 litres of wort at 1.050 specific gravity, they would have actually both had identical kettle efficiency.

(Notice in the above paragraph how 25 x 40 = 1000 and 20 * 50 = 1000?)

So, I'm not sire if you should be adjusting your auto-efficiency at this stage Brandon. It will depend on your actuals on past brews.

Dilutions

The BIABacus is basically warning you that the brew you have planned is too large for your kettle. When this occurs, you have to make some sort of compromise...

a) Reduce the desired VIF - less beer.
b) Dilutions - more grain will have to be bought and depending on when the dilution occurs, quality might be increased or compromised. Dilutions before boil starts may increase quality. During boil is probably neutral and after boil, can affect quality negatively especially if using low quality water.
c) Sparge - using the water you can't fit into the kettle in the mash can be used to wash the grain further but you need an extra heat source, extra vessel and a lot more work. The amount of water that you couldn't fit in the kettle during the mash but can do so before the boil is not a lot so it is nearly always inadvisable to go this route.

In the BIABacus, when you do Full Volume Variations in Section W,you need to think about the above. If we ignore c, then what you want to look at is Mash Volume, Volume into Boil and the total amount of grain needed (bottom right of Section C).

Try, in Section W adding 15 litres of 'Water Added Before the Boil' and then 30 litres. (We have better warnings in later BIABaci but you get the idea.) The reason you get the big warning on the 30 litres is that there comes a point where you really just aren't providing enough water to wash the grain. This is one of the fantastic things about the BIABacus. It tells you when you are asking the impossible. (Other programs cannot do this.)

Not sure if the above is clarifying for you or confusing for you Brandon . Hopefully the former. Let us know if MS or I are helping or hindering ,
PP