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I recently re-fitted my mash tun with bazooka screens (from the braided steel dryer hose) and now for the last several brews I am finding that my volume of wort pre-boil is much larger than calculated, thus my post boil wort is much larger and I have been throwing the extra wort out as it will not fit into my fermentor. Tossing the extra wort can not be good for the rest of the calculations.

I have been using Beersmith or brew365 for water volumes and then volume-metrics to calculate the amount of water in my boil pot. My boil pot has a radius of 6.9", height of 13", which equates to a 8.44 gal volume. I am brewing an AG 5 gal batch today of Weizen and Beersmith is telling me to use 3.20 gal in the mash and 4.80 gal in the batch sparge. So the total water used will be 8.0 gal, the constants in the software is 1.23 lb grain absorption, 82.8% est mash eff and an est 6.52 pre-boil volume. Based on my last few boils, there is no way that I will end up with 6.52 gal of pre-boil wort if I start with 8.0 gal total through the mash and sparge. I recently brewed up a 5 gal batch of Pilsner and Beersmith called for 8.33 gal of total water, I was suppose to get 6.79 gal and I ended up with 7.33 gal of pre-boil wort. I only lost ~1.0 gal in the mash but beersmith calculated a 1.54 gal loss.

I guess my question is, what do most AG brewers use for their grain absorption? And how should I calculate my mash efficiency? Or perhaps I should just start using less water ...........

Thanks, chicanuck

Adapt the water-in in your system to get the amount of wort you want to come out of your system. You're part way through the trial and error phase so why not try again and if you undershoot your volume top it up?


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It sounds like you should use less water and adjust your beersmith settings for your equipment. Everyone's system is different and even when you change something it can throw things off. In the past when I've made changes to my system it could take a couple of brews to adjust.

chicanuck wrote:I recently re-fitted my mash tun with bazooka screens (from the braided steel dryer hose) and now for the last several brews I am finding that my volume of wort pre-boil is much larger than calculated, thus my post boil wort is much larger and I have been throwing the extra wort out as it will not fit into my fermentor. Tossing the extra wort can not be good for the rest of the calculations.

I have been using Beersmith or brew365 for water volumes and then volume-metrics to calculate the amount of water in my boil pot. My boil pot has a radius of 6.9", height of 13", which equates to a 8.44 gal volume. I am brewing an AG 5 gal batch today of Weizen and Beersmith is telling me to use 3.20 gal in the mash and 4.80 gal in the batch sparge. So the total water used will be 8.0 gal, the constants in the software is 1.23 lb grain absorption, 82.8% est mash eff and an est 6.52 pre-boil volume. Based on my last few boils, there is no way that I will end up with 6.52 gal of pre-boil wort if I start with 8.0 gal total through the mash and sparge. I recently brewed up a 5 gal batch of Pilsner and Beersmith called for 8.33 gal of total water, I was suppose to get 6.79 gal and I ended up with 7.33 gal of pre-boil wort. I only lost ~1.0 gal in the mash but beersmith calculated a 1.54 gal loss.

I guess my question is, what do most AG brewers use for their grain absorption? And how should I calculate my mash efficiency? Or perhaps I should just start using less water ...........

Thanks, chicanuck

If you're getting too much fluid then use less water You could also boil longer for more evap but if you're hitting target gravity with the larger volume then you'll want to use less malt also (obviously).

I assume you're batch sparging?

Malt absorbs nearly 1 L H2O per Kg. It varies a bit between batches of malt and types of malt though. Compaction of final bed, overall temperature and other variables all play a role as well. You can't calculate exactly how wet / dry your bed will be so I say forget science and use common sense - use less water.

Are you reaching your target gravity and still have all that wort left over? If you want less, do what Nash said, use less water and less grain.

Also left over wort can be frozen and reboiled to use for starters if you have the room to store it.

Thanks for the replies, I never thought of freezing the wort and reusing, great idea.

Yes, I am batch sparging. At 1L per kg, I can expect to lose ~4.65L (grain bill is 4.65 kg) or 1.23 gal of water. Minus the 8.0 gals, I should end up with 6.77 gal pre-boil and BS claims I should have 6.52 gal or 0.25 gal extra or ~2% excess wort. I will decrease my water by 5% for this brew to 3.0 gal mash and 4.6 gal sparge, then re-calculate my constants.

Thanks for the help, off to start the brew day;)

Decreasing both the mash and sparge volumes by 5%, I ended up with 6.57 gal of pre-boil wort with Beersmith calculating 6.52 gal......a huge success. One or two more brews I will have this locked in.

Thanks, chicanuck