Volume occupied by yeast and trub

[matridium]

I realized something yesterday when I was bottling up my finished beer. After I calculated how much priming sugar I needed I proceed to boil 16 oz of water and corn sugar and dumped this into the bottom of my bottling keg. It was not until after I was half way transferring from the primary to my bottling keg it dawn on me I did not account for the yeast taking up the volume occupying the bottom of the fermenter. The total volume in the fermenter was 4.5 gallons including the yeast but when I measured the yeast, trub, dry hops I realized the volume was closer to probably 4.0 gallons. I’m worried about over carbing the beer. The crazy thing is all the years I’ve been brewing this is nothing I have thought of and I’ve had some over carbonated beers and I bet this is why. Also it’s hard for me to see volume since I usually use 2.5 gallon kegs to ferment in and transfer over to a 2.5 gallon keg to bottle from. I try hard to not allow the beer to have air contact once fermentation starts. I inject priming sugar into the bottling keg. I never know exactly how much liquid I have after fermentation. I noticed this time because I used my 5gallon fermenter snd I could see the yeast... I really suck at brewing beer if this is really the first time I’ve noticed this and how to not make this mistake in the future if I can’t see the volume of the finished beer when I use kegs. I do have 2.5 glass jars that work well as a fermenter so maybe I need to move to it to eliminate this issue?

 

[VikeMan]

I inject priming sugar into the bottling keg. I never know exactly how much liquid I have after fermentation. I noticed this time because I used my 5gallon fermenter snd I could see the yeast... I really suck at brewing beer if this is really the first time I’ve noticed this and how to not make this mistake in the future if I can’t see the volume of the finished beer when I use kegs.

Since you're injecting priming solution into your bottling keg....
You could weigh the keg and subtract the empty ("tare") keg weight to get the weight of the beer.
Divide the weight in lbs by 8.34 pounds per gallon to get the gallons of water that would weight that much.
Then, divide that by the beer's FG to get the volume of beer. Example (using a notional 5 gallon corny keg):

Empty keg weight: 9 lbs
Beer FG: 1.010
Weight of Keg with Beer: 48.5 lbs

(48.5 lbs - 9 lbs) / (8.34 lbs/gallon) / 1.010 = 4.69 Gallons Beer

 

[matridium]

When I switched over to using the kegs to fermentation I actually recorded the empty weight of my kegs. For what purpose I do not know.? Maybe I was going to do what you suggest? Your suggestion makes total sense; and why I did not come to this conclusion? I was not even thinking in this direction when I started to ponder how can I correct this before my next brew. Thanks man!
I have not thought long enough about it but there has to be a way to determine how much water was absorbed by the yeast alone for cellular processes and how much water vapor was scrubbed away with CO2 during fermentation. That would be interesting to know.

 

[Snuffy]

You could go with the fizz drops and forget the whole priming solution calculating and bottling stage transfer. Just *plink* and fill. Never fermented or bottled out of a keg, but I’ve bottled right out of the primary or secondary bucket valve on top of drops quite a few times with good results. I think I’d probably just seal that bottling keg and let her prime right there.

 

[matridium]

I’ve tried the drops before I got good results. Did this years ago when I fermenter in glass and used a bottle bucket. However my move to kegs was to eliminate as much air contact as possible... I have primed a keg in the past but to be honest I don’t like keeping the beer in the keg. Also I have experienced leaks and stuff like that. So frustrating when a leak was there and it was so small you think everything is fine! Then it turns out it did not fully carbonate. I also tried force carb with mixed results. Maybe it’s me? I have force carbed then filled bottles to good results but I had to chill everything down in the freezer and to me it was a big hassle. I then adopted using the beer gun to fill bottles for priming. And let it all just prim in the bottles.
I share lots of my beer and my friends and family like it when I give them a six pack to go home with. If I kept it in the keg I would be drinking way more then I need... anyway. I think the keg weight idea is a good one.

 

[ncbrewer]

I keep track of how much loss there's been on previous batches. Then apply that to the batch I'm bottling when calculating the priming sugar needed. It's pretty simple and consistent enough. Recently I started tracking a couple of styles that have different trub volumes than the rest, but that's just fine tuning.